The short version is 'Don't Be An Ass'.
Which is to say, be polite, don't call someone something nasty and don't be a jerk because you think it's funny.

No Name-calling; this covers pejoratives, racist names and general bigotry. That includes referring to people as retards. Don't do it.

Don't be a troll. If you're the only one laughing, the joke wasn't funny. Keep making 'jokes' like that and a moderator will hit you with the Carp of Smiting.
Don't be a troll - and don't feed the trolls!

.. and for fuck's sake, don't censor words. Tag appropriately for trigger warnings, and don't be an ass.

Politics. If it can't be discussed calmly and rationally, don't post it. Things are shit out there, and I do grok needing to yell about that sometimes, but tag 'em appropriately (either as 'ranting', or some other variant), and remember the bit about being kind to each other.

Artificial Intelligence. Generative AI, LAION, what you have. Not. Allowed. Do not feed posts into the lying machine. We will do our best to stymie the scrapers; don't help the thieves. Try not to post anything created with Gen-AI - I know it isn't easy to recognise it sometimes, but do your best.

Content. I shouldn't have to tell anybody not to post CSAM here, but.. well. Don't post that stuff. Generally, tag content warnings and respect boundaries.

Expect this to be a living document and refer back as needed.