Over the years I’ve gleaned an appreciation of good comment threads! and of what helps or hinders them.
“Please no name-calling”. Labelling someone usually doesn’t get to the essence of what’s going on. Let’s talk about ideas and behaviours. (Please don’t use put-downs on yourself, either.)
“Please speak for yourself from your own life, or else say where you got the info”. This helps people to understand why you believe what you do, and follow the trail back. It also encourages writers to double-check their own sources.
If I think of more pointers, I’ll add them here.