Hard to tell but it could be something as simple as just checking the name. So we just all rename ourselves to Reply Guy to see if that stops the spam.

Could also be that they run on a centralized database which stores the npub from which they send the reply to ignore any events from that npub. 

 So relays can figure out who the bots are by seeing who doesn't get reply bot spammed? 

 Only if the relay is getting reply bot spam directly to their relays.

Otherwise they could observe false positives. 

 that seems a good strategy. I'm just using the names and images in the profile, and it's working for now. 

 that seems a good strategy. I'm just using the names and images in the profile, and it's working for now. nostr.fmt.wiz.biz