Does weird things when most of the people you are talking to are strangers. I think humans brains are built for villages, for relatively stable relationships. Instead you see a stranger write something, you reply what you think, someone else replies to you, you reply to them. Whether you are agreeing or disagreeing, but there's not a lot of actual conversation, just... reactions. HN has a very nice tone, but I recognize like 3-4 names and couldn't tell you if the person I agree with today was the person I thought was an idiot yesterday.
I think for example the most successful communities on Reddit are either mega-obscure, so that there are very few newcomers, or very strictly moderated (e.g. /r/weightroom) in a way that maintains the culture. Everything else is is more or less a dumpster fire.
Dunno if you've thought anything along these lines.