I don't mean humor in general – which is great if you can include it – but the one-liners, puns, and feigning ignorance jokes.
I don't know. I guess I'm worried about that scenario that plays out all the time where someone puts effort into making a good argument hoping for deserved admiration, but then someone else can come along and crack a simplistic joke and in one second get promoted right past the first guy.
If that scenario plays out it not only discourages valuable discourse, but it encourages the opposite. Jokes are easier than thoughtful comments. So if they're rewarded just as well or better, than people will choose that route.
And a thread full of attempted jokes gets noisy fast.