"Please don't post shallow dismissals, especially of other people's work. A good critical comment teaches us something."
"Please respond to the strongest plausible interpretation of what someone says, not a weaker one that's easier to criticize."
I didn’t realize jokes were against the guidelines as well (especially since the joke in question doesn’t appear to be st anyone else’s expense).
Jokes aren't against the rules but they have to be pretty good not to count as unsubstantive comments. Most people overrate how funny their jokes are. See https://news.ycombinator.com/item?id=7609289.