I like your comment and think it could potentially approach the broader problem in a roundabout way, but it does feel like a separate thing. But ignoring that,

I like your comment and think it could potentially approach the broader problem in a roundabout way, but it does feel like a separate thing. But ignoring that, I run a forum and so think a lot about ways of encouraging decent conversation. I think Reddit mostly does pretty well in that (in my experience) the junk is hidden and requires effort to read. Hacker News pushes it down the page, but it's trivial to scroll down and see who's in the naughty corner out of curiosity. I mostly read r/NBA and find the quality very decent. I'm sure there are trolls and racist rants and so on, but unless I expand comment branches, I don't see any of them. I find that the branches being pruned/hidden helps manage how much time I spend on a discussion too. On HN, I often feel like I want to read or skim every comment in a discussion which is rarely a great use of time.