I think you nailed it. There’s two parts: 1) educated users and 2) self-/mod-enforced culture. So far, HN hits both. However, even HN is starting to upvote puns

I think you nailed it. There’s two parts: 1) educated users and 2) self-/mod-enforced culture. So far, HN hits both. However, even HN is starting to upvote puns, engage in group-think, etc. To fix this you must moderate strongly or only allow material that attracts educated individuals.