From what I understand, the mere exposure to slurs reduces one’s sensitivity to prejudice. That is to say, simply hearing a joke or story with a slur makes one more racist/homophobic/etc, at least for a brief time.

The effect was not observed with other explicit language; only slurs.

If that is the case, then it causes harm even in cases where, as you put it, it is “IRONIC or DARK HUMOR context and not meant to harm.”

Personally, I am based in the United States and while I am not usually the subject of slurs, I generally do not prefer them, if for no other reason than to show support for others who are targeted.

Whether it is tolerated varies by instance and community. As a general rule I’d guess it depends on whether the moderator believes your intent is to cause harm. If it is intended to be harmless then it is likely permitted. However, such language would be perceived very poorly - that is how racists talk, after all.

I, for one, would likely down vote it. On Lemmy, many communities are trans safe spaces so those kinds of slurs are not tolerated and will very quickly lead to a ban. Any use of the N-word for pretty much any reason, other than, maybe, quoting rap lyrics, would result in a ban in almost any community of American culture