These days, the only jokes that I've noticed not being downvoted are those that are a certain brand of witty and intellectual. Or they at least give the appearance of contributing to the discussion, even it doesn't survive detailed scrutiny.

This cultural dynamic seems to work out alright, given the other characteristics of HN. It would be hard to do better I think. Overall, I'm personally pretty happy with the level of discourse on HN.

I'm surprised that you are surprised, being a member for 6+ years. Was it different before?