“Instead of generalizing situation-specific behavior to personality (i.e. “Oh, he’s not trying to make me feel stupid, that’s just how he talks”), people assume that personality-specific behavior is situational (i.e. “he’s talking like that just to confuse me”).”
Those aren’t really mutually exclusive. “Talking like that just to confuse his listeners is just how he talks”. It could be an attribution not of any specific malice, but generalized snootiness.
“Everyone on this site obviously has an interest in being, on a personal level, more rational.”
Not in my experience. In fact, I was downvoted and harshly criticized for expressing confusion at gwern posting on this site and yet having no apparent interest in being rational.