"Please don't post unsubstantive flamebait, and please don't post supercilious dismissals." - dang
From the guidelines:
"Be kind. Don't be snarky. Have curious conversation; don't cross-examine. Please don't fulminate. Please don't sneer, including at the rest of the community."
"Comments should get more thoughtful and substantive, not less, as a topic gets more divisive."
"Eschew flamebait. Don't introduce flamewar topics unless you have something genuinely new to say. Avoid unrelated controversies and generic tangents."
"Please don't post shallow dismissals, especially of other people's work. A good critical comment teaches us something."