Fediverse

PieFed allows for this already, though iirc the flagship instance PieFed.social chooses to put nothing for Lemmy.ml.

I always enjoy content on Beehaw. This is the note that appears on every single post in a community on that instance:

This post is hosted on beehaw.org which has higher standards of behaviour than most places. Be nice.

Notice how the link goes to Beehaw itself for additional details, to explain their policies in their own words.

I always found Lemmy.ml's own choice of words to describe themselves quite disingenuous though - as if it were merely FOSS or something being discussed, and as if nothing whatsoever related to politics exists, certainly nothing that might, oh I dunno, differ from their very narrow, highly specific viewpoint (which distinctly clashes with actual facts, e.g. video evidence of the Tiananmen Square Massacre, which tankies declare variously that it did not happen, or if it did happen then that there were no fatalities).

Hexbear at least is extremely open about how they exist for nothing more than the sake of arguments - that's arguably fine even, so long as it remains constrained inside the communities designated for such - where the members actually want it, i.e. consent should matter - rather than spilling out into every single other fucking community all across the Fediverse.