Earlier quoted context omitted.
I also think the lack of consequences makes it very easy for people to post all kinds of shit. On HN this is greatly reduced by the point system and the opacity of bad posts. A bad post fades away so it doesn't look as important as other posts. In real life you can get a punch in the face if you say nasty things to someone. But on Twitter, Facebook and YouTube most trolls wont ever learn because they just can say wha…
Worth considering that this isn't simply mechanical: to make those posts fade away requires humans clicking the downvote button. Which requires some kind of culture that includes clicking the button on "bad" posts, for whatever the definition of "bad" is. If there were downvoting on say, YouTube, I'm not sure that it would produce the same results that it does on HN.
It is worth remembering that the visible part of an internet community is a small part of the total possible community. Following the classic 90-9-1 rule there are a lot more people who could participate than people who do participate. This means that the visible face of an online community has a lot of room to change.