New to the forum. Being an INFJ myself, I felt the need to include my two cents.
Since I can (at times) be a pretty emotional person (mix my PMDD with my INFJ), I tend to act on a whim, meaning I'll do things spur of the moment and regret them greatly later on. In response to the original post, the girl may have been embarrassed about the wrist cutting thing and didn't want to talk about it. I know I get embarrassed when I'm called out on my irrationality, especially because I know it's irrational; and yet I can't control it.
So, embarrassment is one reason why I might doorslam, but this type of doorslam is usually never permanent for me. I'll come back around and start talking to the person again someday, after analyzing the relationship and coming to the conclusion that it is "safe" to rekindle it.
I doorslam permanently if someone has extremely crossed the line. However, that doesn't mean that they don't cross my mind on several occasions (i.e. I wonder how "so and so" is doing). I also find myself contemplating on trying to rekindle the relationship, even if it is a horrible idea. I strongly dislike several people, but that doesn't mean I don't wish we could still be friends. I guess my feelings for other people play a huge part in that.
In addition, I have never doorslammed an ex. I find it hard to just cut off a relationship that I invested so many feelings into. It's impossible for me to just "disconnect"... at least until I'M ready to... but it has to be my call.