Those are bots someone has created to post their spam crap as replies to random posts. I don't know that there's anything you can do other than just block the accounts doing it.

I think this is going to be a growing problem for Nostr. Since anyone can create unlimited accounts instantly, it's ripe for abuse. Not sure how you could implement a decentralized spam blocking system that doesn't also create an avenue for censorship.

I'd like to see clients that let you block posts by keyword. So if someone is running a pump and dump scam with some new shitcoin and trying to promote it like this, you could just automatically block any post that has the name of the coin (like "zkSync", for example) in it, for example.