On Zapddit another Reddit style client they work by hashtag from what I see and by how many zaps a note gets as upvote/downvotes are handled by zaps. nostr:npub1wj9l4p7yx7efg9jdz7ztxf9q6t55jhyzdrsqgn3uw7t28v2ce8vqnuhet9 or nostr:npub1ltx67888tz7lqnxlrg06x234vjnq349tcfyp52r0lstclp548mcqnuz40t would be the best to talk to regarding their implementation and how everything works.