[muzani]

Algorithms generally reward "unpopular opinions" - polarizing views held by a minority.

Facebook, without its downvotes, doesn't punish them, so people can be as cynical, bitter, and savage as they like. The algorithm boosts these. Some have a downvote button, but by giving more weight to upvotes, it has a similar effect.

Reddit rewards groupthink. It self-selects clearly enough into subreddits. X does this invisibly by grouping people with similar opinions.

HN is a mix. The main topic itself has no downvoting mechanism, so most people will disagree by writing comments. If 1000 people agree and 300 don't, you'll see hundreds of comments disagreeing and few agreeing. Since people come to the comments to downvote, the cynical opinions float up.