Why can relays use it but clients cannot?
Discussion
Relay operators are responsible/trusted to verify reports. There is no client operator. You can take the responsibility as the developer but in this case the system will be gamed in accordance with how popular clients are programmed.
I’m not totally against clients using report data. But great care should be taken.
Bullshit, relays aren't in any position to do this
It’s literally why the report system exists. Regardless, you don’t get to run a relay without being responsible, and obliged by local laws. The censorship resistance of nostr lies in the fact that you can just connect to another relay, not that every relay must serve everything.