It would probably be something that fediverse instance admins ought to put in place, considering the dark turn that the Nicole thing has taken. Dual purpose: prevent spam/scam/bot accounts, offset hosting and administration costs for a platform that should remain otherwise unmonetizable.
I’d pay it.
Very recently, some people started receiving images that allegedly show a grisly murder. (I have not seen such an image myself. I can’t speak to whether the image(s) are “real.”) Bad enough that the main Nicole comm got locked down, and people are wondering whether law enforcement should be involved.