Where does this perception come from? HN upvotes humor all the time, the bar is just slightly higher than some other sites - which is IMHO a good thing because endless pun threads quickly become tiring.

I see humor downvoted all the time, with occasional lecturing of how it’s not appropriate here. Not to mention the chastising you occasionally see for not using an overt sarcasm indicator (Some folks are strangely zealous about that one).