Dang has spoken about this at some length in interviews, but the critical element is whether or not we're all seeing the same thing or not. HN is special in the world of social media because the front page is the same for everyone. That makes it quite a bit different than other social media sitesfolks mention (Twitter, Bluesky, Facebook, Insta). It means the algorithm can be tweaked for engagement (like demoting stories that have more comments than upvotes), but that you can't optimize per-visitor, but instead across the whole population. That one simple feature makes a world of difference, in my opinion.