I think people really tend to undervalue good moderation and related systems for shaping good discussion. It's extremely common on HN to see people write off all moderation as censorship and an absolute bad, but then it's really interesting to see that so many people repeatedly pick the very-moderated HN over places like 4chan. It's like fish, ignorant of water, proposing that it's universally true that decreasing the obstacles and material between each other improves the discourse, while ignoring that places like that do exist and largely lack that benefit.
It has to do with culture. Take traffic precautions. People stop speeding when you place speedbumps. You might need those speedbumps for 5% of traffic users, but it useful. Nobody has claimed that there is a speed dictatorship.
The same goes with moderation. You create a culture where you allow everyone there say, and add specific speedbumps (rules) where your community needs it. Otherwise you get the 5% that overruns the place, skewing the discussion disproportionately.
Is HN "very-moderated" though? I've got my share of unpopular opinions but nobody has ever tried to shut me down over them - something that I've seen happen to myself and others relatively frequently on IRC.
I think it's possible to have good discussion on places that are very loosely moderated, but it's not as simple. And I don't think it can work on sites like 4chan where user have no identity
