yep, clients could easily implement basic auditing thanks to nostr's event history. basically zero code. you don't even necessarily need manual, prose reviews - a positive paper trail of pro-social behavior goes pretty far. (of course, implementations could add reviews trivially as well with existing Kinds. this could be a distinguising feature that might attract users to your client)
GrapeRank is the ultimate end goal. but we can get really far with just basic nostr events for a while.