This is going to be a long response, sorry...
That's helpful.
One of the things that is bothering me in all these descriptions though is that there is an implicit blaming of all the relationship problems on the other person. It's as if the INFJ is saying I've done everything I could and am just not being treated the way that I should (whatever way that supposedly is which presumably is unique to them as an individual). Relationships are always a two way street and it's rare for stuff to be all one person's fault. To blame it all on the other person is wrong.
I hope that's not the impression I am giving off. I can freely acknowledge that my poor emotional regulation worsened both of the situations I've talked about. Until late last year I had clinical depression and was in a very destructive Ni-Ti loop, so lacked the emotional maturity to truly love someone else. I couldn't give much. At the back of my mind was the knowledge that while you can probably always do more, you must take care of yourself before you can another, and the girls I was dating were in the same situation. Mysterious with a tragic past (which
superficially sounds very attractive). Can you imagine how exhausting it is absorbing negativity from someone you're trying to feeling attracted to and aroused by, often, when you're feeling like utter shit yourself? Sex isn't fun either because both parties only want to take - be held, comforted, transformed - but can't provide that transcendence to their partner.
This is the cruel nature of depression, it wrecks havoc in relationships, as I found out. And I would say I've had a bad track record of codependent relationships. Look up E4 at Level 7 to 8 of health, that's what I was like until very recently. I am at Level 5 now.
As to "loyalty" - the behavior seems to be the antithesis of that. I have had an INTJ friend since college. Sometimes we don't talk to each other for years at a time. He stays with me thick and thin. I do the same with him. That's loyalty. Bringing someone in really close and then suddenly dumping them on the side of the road because the relationship dynamic is hurting you isn't loyalty. It seems like dis-functional relational behavior due to a failure to set normal or appropriate boundaries and an inability to to deal with conflict in a constructive manner.
Unlike our INTJ cousins, INFJs can't "not talk" for years at a time because we have a strong need for intimacy, which, at least for me, means frequent sexual contact merged with an emotional commitment. I want love, I want to get married and have kids. If you want me to be upfront, the reason I doorslammed the girl I did was because she kept delaying "rites of passage" in our relationship yet had no qualms toying with my emotions, leading me on with sex only to disappear for a while (or at least that's how I interpreted it). I have a strong need for security in relationships (4w3, 6 fix) and have posted elsewhere on the forum about how deeply I loathe flaky, avoidant women.
I will also qualify that I have never "brought someone in really close" only to dump them. The girl I doorslammed was very much attracted to me, but we'd only been going out for a month and there were some things about her past which always made me highly uncomfortable...like that she'd just decided to move over a thousand miles from the other end of the country down here, without an explanation...that was her story

I might elucidate in my blog sometime.
FTR: I strongly suspect she was also an INFJ 4w3 actually, very very similar personality to me. Too similar...which brings me back to my point about complimentary traits, growth, and what we need. Learned this the hard way - ESTP women here I come
