On HN, humour is almost only ever desired if it's in combination with other content. If someone injecting a bit of humour is not quickly downvoted, then others start throwing out their "witticisms" and things degrade rather quickly. Better to nip it in the bud and potentially upset someone making an innocent comment than to have things overrun.
I think people want high SNR value before a clever triple entendre, but accomplishing both is far better. Failing that, expressing a clear, reasoned sentiment is also another tact.
