I've recently decided I'm INFJ so I'm gonna try to contextualize these according to my own life/perceptions if that's OK.
Misunderstandings:
1)Delayed processing time - INFJs often seem to be basing their responses to the person in question on the last interaction they had with them, more often than the current one. They prefer to have time to think things over, which is why it's not a great idea to try to push an INFJ into making a decision before they feel they have had enough time to mull everything that has been brought up.
This is one reason I'd previously considered myself a P. I do indeed have an annoying habit of hearing everything people say in the context of something they have previously said; for example, my mom was talking about how being a parking inspector looked like kind of a fun job because you're outside and get plenty of exercise, and I immediately assumed she was judging me for not getting enough sun (which she had done earlier that week, but totally didn't mean it that way).
2) Need for resolution - What may look to some like being nitpicky or unforgiving or even holding onto the past often has more to do with their need to get everything put away in it's proper place before closing the chapter on it. Without doing so, it keeps coming up again and again.
Sometimes, I distance myself from people who aren't willing to come back to some fight we had in the past, because I can't stop thinking about it when I'm with them.
3) Considering every hobby, person or idea expressed as an extension of themselves - INFJs tend to be very self-protective, and rarely bring something up unless they have already implemented it into their main framework of thought or affection. Therefore when any of these things are dismissed or mocked, they will feel it as a personal rejection, unlike someone who tends to verbalize new ideas out loud. Similarly, INFJs will sometimes be confused by someone who seemed committed to a thought or a plan, only to abandon it later.
Nothing's more frustrating XD again, coming back to my mom, sometimes we'll decide to go to see a movie and then she'll decide she doesn't feel like it an hour or two ahead of time and just cancel

I can understand if it happened once in a while but we hardly ever get a chance to do things together because of this!
I'm relatively open to being wrong, though, I think. If someone puts forth a point that I'm willing to admit I hadn't considered, of course I'll have to re-assess.
4) Dislike of emotional surprises - this leads INFJs to sometimes inconvenience others in their effort to know what to expect. I'm fine with a change of plans, but find it harder to quickly adjust to someone's sudden annoyance, to a change in something I had really been hoping for/counting on etc. Makes me more likely to try to be the one to take on any inconvenience because that is more predictable. I also tend to need to watch a situation for awhile (either social or skillwise) before I am comfortable jumping in. I think with maturity we can become less focussed on their own reactions and feelings and also realize that someone else being upset is not the very worst that can happen. Sometimes avoiding that happening actually creates more conflict.
Hm. I do this for other people as well - when my mom flakes out on my brother or sister, I try to pick up the slack. Of course, then she starts to take advantage of that... I'm not sure where this will lead. You're right that it has caused conflict in the past, which I wasn't expecting.
Observing 'til you're comfortable - sometimes. I do tend to read a lot of posts before participating (the whole thread, if it's short!) but on the other hand, I often don't want to pollute my own viewpoint with those of others before I post it because I will definitely lose track. Hence what I'm doing right now

In social situations, or, like, with a video game and so on, I do prefer to watch someone else to figure out how it works before I start developing the skill or introducing myself. Model before experience, sort of thing. Unless, of course, the 'point' of the game is to start and figure it out on your own. :s
5) Hold those close to them to a higher degree of accountability than those that are less important to them - This may seem judgemental and unfair, but because those close to them are an extension of their own self, integrity is paramount to them and they choose to invest heavily in a few close relationships, they expect more of those people than they do of casual acquaintance friends. When they feel you are worth risking conflict with and you start hearing the negatives about yourself as well as the positives, you're in!
eheheh... <.< not everyone appreciates that... "How come you're not this critical of anyone else???" ~ direct quote
"I am... I just don't care about them as much as you."
Of course, online is a different story...
Actually, sometimes I take on 'grasshoppers' to try and 'straighten them out'. I can be really critical of those too, even if I'm not emotionally committed to them.
6) Easily embarrassed and quite private - May mean that they take awhile before talking about something that is painful to them. This doesn't mean they don't care about the support you could give them. It's just that they need to get it thought out in a framework and untangled before they are ready to be more open. I tend to talk about it more after I think I'm going to be alright.
Unfortunately true. My dad can instantly tell when something's up but I can never seem to tell him what it is until I've got it figured out. I've been trying to express things at an earlier stage with him lately, and it just comes out all useless and makes me feel even more inadequate because I know he wants to help and I can't seem to give him what he needs in order to do that.
7) Long gaps in correspondance or putting off a job that matters a lot - This seems to be linked to wanting to do an excellent job of it and feeling overwhelmed by the amount of time or effort or organization required. The longer it is put off, the worse we feel. As a result, it is usually my most valued friends that I correspond with least. Usually I try to overcome this by phoning them, catching up on the bulk of it, and then writing the rest.
It is really tough. I have trouble buying presents for people because I want it to be something really heartfelt and meaningful. To me, a box of chocolates says "I don't really know you so here's a generic token." So quite often I end up missing the occasion entirely. This was a major source of strife between me and my aunt.
Tendancies:
8) Not creating clear enough boundaries for people around them - there's a tendancy to respond to those who are most actively demanding attention, especially when younger. Also the need to be sure that they've looked at everything from all angles, made a correct assessment of all possible motivations and exhausted what they can do to impact the situation before really drawing a hard and fast line. I think this improves with age.
Yep, 'calling in the mods' is really tough since I always think there's the possibility of reconciliation. I used to do it a lot when I was little (think grades 1-2) because I didn't have any other tools, but nowadays there's just too much to try.
My therapist was telling me this exact thing, actually. I think and act like I don't
have boundaries, but I actually do have some very clear emotional ones which I should externalize instead of just keeping quiet and coping every time they're crossed.
9) Find it difficult to assess when is the time to make a Big Deal out of something - Their reaction to something really depends on the other person's response. They may find it easy to forgive something or deal with it on their own if the person recognizes that they are making a concession. If the person trivializes or continues on with more of the same behaviour, it's the last straw (in a very big load of straws!) and the other examples of where they have seen the same behaviour will be brought up.
oof. Too many 'yesses' to just pick one as an example. I only end up in big fights with people over things that are really important to
them, even if they are only minor grievances for me :s
10) Hate being not in control of their emotions, yet sometimes underestimate how strong those emotions are till they are swamped by them. - (Note, not a good time for Ts to talk about how over-sensitive and emotional they are, as they despise being that way and are already terribly embarrassed).
Not sure about this. Especially since I'm nearly T anyway, I'll leave it alone.
11) Get less receptive to advice if the other person tries to skip over the venting that they need to do in order to bleed off excess emotion or when they feel the person hasn't taken enough time to understand the situation. Often their solutions are gained primarily from discussion with someone, not from getting the answers from someone.
The latter is certainly frustrating for me. As for skipping the venting, I really try to avoid venting anyway, and when I do, it's in a very short, explosive burst that doesn't really leave room for interjection. This is due to a book I was given in my teen years and I find it fairly effective.
12) Sometimes have a hard time recognizing when they need to pull back or give less so that they can continue doing so cheerfully. This seems to be the case especially with Ts.
I do sometimes feel like I'm being too nasty even though I'm genuinely trying to be nice

if this is what the problem is then I guess I have some work to do.
My own (maybe INFJ related) problems
13) Tendancy to be poor with paperwork, locating items quickly under pressure - I've largely solved this by having a big lanyard for my keys, carrying a decent sized purse and having a file folder that things go into immediately.
Kinda. I got good at searching for things because my entire family has ADHD-PI (including myself, of course)
14) Am a responder more than an initiator - as a result I've missed out on many good friendships. I've learned that people respond much more warmly when you go out on a limb and make the first move. I've been working to actively improve this.
Yup. It's hard but worth it! Seriously, I've started initiating like once a month at most, but it makes people so happy :3
15) Not good at paying attention to detail (in my environment, and in instructions) - This is why I try to stock a lot of sensors in my life. They are happy to fill in my gaps and give me reminders when needed. They also tend to think in terms of smaller practical details that must be attented to.
I tend to remember details that seem salient to me at the time, but then I get into the actual process and totally miss something they said was important. I have trouble remembering a set of instructions though, which is why I try to abstract it into 'sensical' steps.
16) My intimidation by Te, and some oversensitivity leads me to sometimes not express my opinions when I should - working on this one. Thinking it out ahead of time helps.
It certainly does. I've gotten to be able to mirror it in online debates - face to face is a little tougher, though.
lol. a lot of people at INTJf sight-type me as INTJ because I come across as very Te-heavy to them. Of course the exceptions quickly diverge from the main thread into rep comments and PMs, so they don't see how much different it is
17) Over-indulgent when under stress - eat bad food and buy make-up/magazines that I don't need - Am working to replace these responses with exercise, drinking water etc.
Fancier coffee and fast food, fa sho. Drinking water is a good start. Exercise seems out of reach for me though >.> Going outside and running around the block to help concentrate is about the limit.
18) Put off jobs that are unpleasant or that I am not sure how to do - I'm sure this isn't totally type related, but I think avoidance is a greater tendancy with INFJs than Te driven people. Sometimes Ni and Ti create a loop that doesn't work well.
Hah. Especially the 'not sure how to do' part. For some reason I'm really scared of calling one department if I don't know whether that department can handle my request - even though they can usually just redirect me to someone who can. -.-' Once I know where to call, it's not hard at all.
19) Stubborn - I tend to need a lot of convincing with a new idea before I will adopt it, because it involves changing the whole structure over again.
I'm sure others think this of me more than I think it of myself
20) Promising more than I can actually deliver - I want so badly to take care of everything that sometimes I overestimate what I am able to do. I've learned as a teacher to promise less and make sure I actually do it every time.
Yup, and it's not even about overestimating what I'm
able to do - but rather, overestimating my ability to remember it, schedule it, and get it done. If the schedule is set ahead of time (and I don't accidentally double-book), it's usually not too bad.
21) Lazy about figuring out technological stuff or leave it to others - This one probably isn't INFJ related. I usually wish that some nice ENTP or ESTP is around to give me the Cliff's Notes on something new. While I am very curious about some things, I am not interested in discovering something for myself because I enjoy the process.
This is another thing which convinced me to switch from NTP. My cell phone isn't loaded with apps, and I only put something new on it when I feel like I need it (and sometimes, not even then, cause I can't be bothered to try all of the options and pick the best one.) This makes me feel a bit like a poseur geek

but the stuff I do know, I'm top-notch. So I've got that going for me

I do like to explore things, but it's usually when I have a vague idea that I'm looking for something in particular, like figuring out all the page layout settings in Word when I'm trying to get the paragraphs spaced a certain way. I much prefer to have, for example, an IRC client recommended to me than go hunting for one or code it myself.
22) Sometimes my very closest friends may feel that I disagree with them but don't express it. That is occasionally true, but if it is not a huge issue of integrity, I'm not sure how expressing it would be helpful. And yet, I don't think that I have to change my mind about it either, as long as I still like and respect them and am not being passive-aggressive. I think INFPs are much better friends in this respect.
I do tend to express a disagreement if
1) it's not relevant to our relationship, and
2) it's something I know fairly well,
because that's what's expected in my circles. Things like someone bullshitting about genetics, I don't mind correcting them. But it's a very...give and take sort of thing. I'd rather correct them in a way that allows them to keep their dignity... e.g. "well, I think you mean that they aren't
self-sustaining rather than that they aren't
alive" - so they can say 'yes, that's what I meant, thanks.' and continue on, rather than getting into a fight about it.
I'm wondering if any of these traits are influences by enneagram (1w2 so/sx) or if they fit with other INFJ's experiences (or those of other types with INFJs). Oh yeah - and did I mention long-windedness?

...
Who knows!!!