> people will engage in thread arson to kill submissions they don't agree with. When I see some of these low value comments, I check their comment history and often they have reasonable comments on other things

I think that's probably overinterpreting. No doubt there's a long tail of weird behavior, but the fat part of the distribution is covered by a simpler fact: humans change when emotions get activated. People who have interesting things to say when their curiosity circuits light up have entirely different things to say when their amygdalas are inflamed.

Edit: their right amygdalas, that is! it isn't clear to me what the left one does but it's a puzzle why everyone says "the amygdala" when we all have two.