Personally, I tend to think that "rewrite entire personality and accessible memory-space and also you're at least a little crazy/believe your own hype" counts as a fairly significant quirk. Possibly include a bit of "reacts Really Quite Badly Indeed when base assumptions are challenged."
I don't really think we need any quirks beyond what we've already seen on-screen (and honestly, would we really want the "break the Haruhi with Truth" storyline that the more blatant quirks would be required for?)
I don't really think we need any quirks beyond what we've already seen on-screen (and honestly, would we really want the "break the Haruhi with Truth" storyline that the more blatant quirks would be required for?)