I think there's a HN cultural preference to avoid stream-of-consciousness tangents, so even clever or informative -- but off-topic -- replies to such tangents tend to suffer.

IMO this is the source of some people's impression that humour isn't welcome here. My experience is the opposite - on-topic (and funny) comments do well even if only a joke or quip, but off-topic humour sinks, even if clever and civil.

I'm quite lowbrow and really enjoy the more clever comment chains on Reddit, but I also appreciate the HN alternative, where attempts at pun chains, etc. sink to the bottom and on-topic thoughts rise.