Since most clients don’t check signatures I think it would be good to have a public test tool / gag relay that posts a bunch of random stuff pretending to be from people you follow.

Like

“jb55: I hate puppies. I really do. I’m that evil.”

And then several line breaks and a disclaimer “this is an impersonation attack test tool. this message wasn’t written by jb55. if you’re seeing this message, then your Nostr client doesn’t check signatures. be very careful what relays you connect to or you may fall victim to impersonators and phishing scams.”