I don't really believe people here are atypically rational, at least I haven't seen any evidence for it so I'm going to assume they behave just like on every other forum and use the vote buttons emotionally.

From my observations, other than spam and other garbage, negative score on Reddit almost always means violating some groupthink taboo. Annoying people by violating their taboos doesn't count as "screwing up horrendously" according to my criteria, self-censorship on the other hand does. I know being nicer in tone lets me get away with violating some taboos, and it pretty much doesn't matter for groupthink-aligned comments. That's less problematic than self-censorship of content, but it's still groupthink-directed adjustment of my comments, something I would rather avoid.