I haven't read most of the recent round of posts on this subject (doorslamming/INFJs/Fe), and I don't want to get pulled into a discussion. I just want to do a drive-by posting and drop off a personal impression and then back out of the discussion as quickly as possible.
Thus:
Everyone cuts off friendships when relations become problematic. If it's true that INFJs do it differently from others, then I think this is because of the way that INFJs form friendships in the first place. Comparing non-INFJs vs INFJs:
Non-INFJs tend to be kind of cold at first with new friends and only warm up slowly. And if there comes a point where it becomes necessary for a non-INFJ to cool down or break off relations with a new acquaintance or friend, it's not a big deal to cool the friendship back down again; the non-INFJ probably isn't invested heavily in the relationship in the first place.
INFJs, on the other hand, tend to come on warm and cordial with new friends and even total strangers right from the start. So if there comes a point where it becomes necessary for the INFJ to cool down or break off relations, it can seem a big contrast: The INFJ seemed like they really liked the hell out of you, and suddenly they're acting cool and aloof.
IOW, the difference lies in the contrast between how the relationship starts and ends: with non-INFJs the contrast isn't so great, whereas with INFJs the relationship is so warm right from the start that a cooling-down phase can seem rather cruel and out-of-the-blue.
I think the nature of Fe itself is part of the issue:
Fe seeks harmony and is empathetic. But it's also an organizational (judging) tool, like Te. So Fe-users tend to be exhibit a certain hot-and-cold aspect: Fe-users are empathetic and warm in some settings, but also rather cold-bloodedly manage relations and keep people at a distance in other settings (the "tier mechanism"**). When Fe is in the Dominant position, the contrast can be rather striking: ENFJs in particular are noted for a disparity between demonstrating a lot of personal warmth while simultaneously staying somewhat distant, to the point that they are often accused of glibness or insincerity in their relations with others. ESFJs are similarly very warm but also accused of being suffocating or even bullying. As for Fe in the Auxiliary, INFJs and ISFJs are noted for being cordial and empathetic but can also be avoidant at the same time.
Just for comparison: Fi works similarly. Fi is value-oriented. But it's also an organizational (judging) tool, like Ti. So Fi-users tend to exhibit a certain hot-and-cold aspect: Fi users are charitable/altruistic in some settings, but also seem very selfish or self-indulgent in other settings.
It's just the nature of Feeling; as a judging function (an organizational tool), Feeling can be schizophrenic (hot-and-cold) in how it gets exhibited to others.
To sum up:
Fe is a schizophrenic, hot-and-cold function. In INFJs in particular, it shows up as a cordiality and warmth early in the relationship that may create an impression of great investment in the relationship. But subsequently Fe will appear in its other aspect (managing relations and keeping people at a distance, IOW, the "tier mechanism"), resulting in a cooling and pushing-away that may be very unexpected to a non-Fe-user and come off as insulting or even catastrophic by contrast with the previous phase.
Just my personal impressions, of course. Okay, I'm done. *Backs out of the thread quickly.*
** The "tier mechanism":
http://www.typologycentral.com/foru...7846&page=79&p=2138075&viewfull=1#post2138075