In my opinion, many reddit-esque comments are genuinely funny. I love pun threads. I'm amused by self-referential hipsterish humour. Etc. This, it turns out, is not relevant.
It's not relevant because funny joke comments are worse (from the perspective of ideal HN behaviour) than unfunny joke comments; it's the funny ones that get more replies, and that means more off-topic noise hiding the on-topic signal (where topicality is defined in newsguidelines.html).
It's not relevant because funny joke comments are worse (from the perspective of ideal HN behaviour) than unfunny joke comments; it's the funny ones that get more replies, and that means more off-topic noise hiding the on-topic signal (where topicality is defined in newsguidelines.html).