quotingProof of Work doesn't solve spam because spammers have more PoW than regular users. In Bitcoin it is effective because its 1 against the cumulative PoW of all others. Also, its effective against redoing history, not spam - see ordinals.
note1rap…cunx
There is no cumulative PoW in nostr, so easy win for the spammers.
Fabian on Nostr: This one also nostr:note1rap4nm306h7y9998m8xukm0ncq53379ryhcl80g6vq90q2n4d4cq5gcunx
This one also