Are Enneagram 4's especially protective of their self-image? Do they dislike it when someone points out something about themselves that's not in line with their self-image? It's probably true with everyone, to some extent, but is the degree to which they do this pronounced in them? Are they bothered by some of these observation because they are true, or are because they are false?
I am aware that the truth can be used as the weapon, and there are occasions where I do this. There also may be occasions where that is either not my intention, or I'm not fully conscious of what I'm doing.