What can get you banned from this website? You don't have to really say it just talk your way around it.

Which website? CSAM is probably the fastest for 99.9% of instances, but Lemmy all federated, and rogue instances can exist outside the commonly federated instances.

Which website? You're on piefed.social, but posting on lemmy,ml.

If this is confusing, that's fair. Federation is a new thing. It's multiple websites that work with each other, so nobody has total control.

Maybe the answer, then, is "nothing". It's whatever your instance (website) will allow. If it allows too much, it itself might start getting blocked by other instances, or even shut down in real life. That's it, though.

You should probably ask again at !piefed_meta@piefed.social, for practical concerns, as this is for questions about your instance, specifically.

Cheese pizza is probably one way to get yourself banned (at a minimum)

Depends on each instance's rules, based on what you are referring to.

Account ban? (You not being able to access your account at all) Refer to your instance piefed.social's rules.

Communty ban? (A community within an instance banning your participation) Refer to said community's rules.

Can't interact with an instance? (not being able to interact with all communities using the same instance) Said instance might have defeferated with your instance; contact piefed.social's admins for clarification. Both parties should be in an agreement for them to federate again.