Is it any surprise that the shittiest new arrivals are from the Fediverse?
Discussion
How can you tell? Who are they?
I think there's a bridge from some of the shittier Mastodon instances to nostr now. You can just tell. Antisocial edgelord comments, racist posts, anime PFP's...oh and they talk about the fedi in their note feed. Luckily, hardly anyone uses Mastodon, so it should be a pretty easy social graph to clean up with a few mutes/blocks.
And since Mastodon sucks, they'll probably just all be migrating to their own relays soon. Zero effort blocking there. Just don't join their relays.