The answer is heavy handed moderation. You need active moderators who discourage toxic comments and commenting patterns, and give out punishments to repeat offe

The answer is heavy handed moderation. You need active moderators who discourage toxic comments and commenting patterns, and give out punishments to repeat offenders. I don't know the the guys at HN do it since there are so few of them, but I like their method of leaving a comment why someone's comment is toxic (usually against guidelines).