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, for practical concerns, as this is for questions about your instance, specifically.