No, I think closure and grudges are completely different. Grudges are an issue of immaturity or handling things badly, not type.
Oh, okay. That's good to know. I had read that INFJs hold grudges longer than most other types, but hearing this from an INFJ helps.
Re venting: In that case, I would like to use this as an excuse to thank you for so graciously listening to my venting about my ESTJ who was in a rather bad place and not representative of typical healthy ESTJ behaviour. You really did perform a very valuable service and I'll never forget it.
Aw

Thanks for the thanks! Of course,
1. it didn't seem like venting at all to me, as much as it seemed like you stating the facts (which might have to do with the fact that everything was typed and not spoken aloud), and
2. you actually considered my advice!

That was courteous of you. Finally,
3. the fact that I helped at all is what matters most.
I actually don't mind advice, but I want to be sure that the person has taken the time to fully understand the situation and waited until the emotional storm is over. I do find other people's perspectives useful and they often affect me more than they may original believe.
That's good to know - it means I'm at least doing something right with the INFJs* I know. If I cut in, in the middle of the venting, it's only to ask "Have you tried...?", which, for the most part, is just to collect information, and not to cut you off. Also, sometimes my mom will say something along the lines of "Please wait until I'm done before you say anything" before she starts on a vent, which is very helpful for me.
Re opening up: It is not a manipulative tactic (see how upset I am, but I won't tell you why because you should know if you're a good person). It's more that I may have to interact with the person, I'm trying desperately hard to be normal and not to indulge in alarming displays of emotion without anything solution-based to offer. I hate crying in front of people or being dubbed over sensitive by people I care about. In the ESTJ case, they are too good at hiding how they have been affected which leads more transparent types like myself to think they really don't care or that they are doing more fine that they really are. I'm not sure whether it's better in that case to leave them alone to deal internally (which seems to be more the T way and the Fi way) or to try to pry a little (which is what I want people to do with me).
1. What's especially strange about the ESTJ thing (and probably counterintuitive, from INFJ standards), is that, even though we don't always make conscious efforts to hide how we're feeling, those unconscious efforts serve the needs/wishes of our conscious mind really well. Just like you, fidelia, we'd rather act normal, and our subconscious obliges. It's amazing stuff.
2. You have two contradictory, though I'm sure no less valid, statements in the above quote. One is that you just want to look normal, and the other is that you want someone to pry a little bit. I find that really interesting, and I relate a little bit. Do you think it's a combination of a 1-ish need to be in emotional control, and an INFJ-ish need to sort your feelings out verbally? If I'm totally off base, I'm sorry - I'm only just starting to learn your language.
In his own way, he tried to be supportive, but he got frustrated if he couldn't just fix it immediately and make it go away
I relate to this a lot, from my interactions with my ex-roommate and my mom. Which leads me to another question: I don't know if this is normal for INFJs, but I've noticed that, with the INFJs I know, when they're in a bad mood or have had something bad happen to them, they portray it in an incredibly grim, pessimistic, evil-triumphing-over-good kind of way. When I hear them vent about it, there is no way for me to know what's feeling and what's fact, and so, because when in doubt I take what people say as fact, I end up just as depressed and pessimistic as the INFJ. And that makes me frustrated because it makes me feel like there's nothing to be done, even though I'm sure there MUST be something that the INFJ hasn't mentioned yet! But there's no way for me to cheer them up that I can think of, because my usual methods of comfort are 1. giving advice, and 2. helping people put things in perspective (i.e. balancing the negative with some sort of positive), and I was not given enough evidence to give advice OR find a positive thing. (Not sure if this was exactly how your ESTJ felt in those situations, but it explains my frustration.)
So, finally, my question is... what am I supposed to do in situations like that?
Probably the difference is that even if ESTJs don't have an argument on hand, they are very good at thinking on their feet and making up one as they go. I remember seeing my ESTJ totally pull things out of his butt that had I not been aware that it was not an area of his expertise, I would have assumed that he knew what he was talking about.
I can't believe I'm saying this, but I think you give him too much credit. I would actually argue that I'm not that good at "thinking on my feet", and I was told by an ENFJ friend that I couldn't BS to save my life. What it is, in my opinion, is thinking out loud. Your version is venting, and our version is pontificating about something and seeming authoritative.
re your INFJ ex-roommate:
I probably shouldn't have brought it up. Yeah, it was a habitual thing, and it was always something really intense. Her dad had died mere weeks after school started, and the little one-sentence things she would bring up would be things like nightmares about her dad, her mom not being supportive, suddenly becoming the manager of her dad's old business (that she knew nothing about) without her consent, feeling suicidal, having fights with her horrible boyfriend (whom she is still in love with when he doesn't deserve her), etc. etc. etc. It became a cycle of guilt for me, because the only time I'm good at handling the hefty issues of friends are when I know those friends very well, and I didn't know her well at all, and I felt like I shouldn't have been having that gut reaction of "Stop loading this on me! Save it for your therapist!", when I actually DID like her a lot and DID care about her, but just didn't feel like I could vicariously handle that pain and suffering.
That is why I will never be a psychologist...
* That was an edit! It said ESTJs before. Pardon me!