I haven't spent too much time on reddit but there anyone can freely post (with enough karma and shit) and the mods can later take it down. However as I understand once a nostr event is signed there is no going back. Relays and clients can decide to delete or ignore but the signature can't be withdrawn. (Please correct me if I'm wrong.) If this is the case then there's this fundamental difference which prevents nostr function like reddit does. Not to mention the trolls who like to abuse NIP-72 rn.
Also as nostr:npub1qfkcklnmes45z75y7y8dkud5yll8vp5eq5ysk9rmgqdxeasv8unsrfj6kq mentioned elsewhere a community post that is not approved can be seen anyway under Pending and in Global too, basically the approval stamp is just a gimmick so what's the point in the first place? (Don't get me wrong I'm not arguing with you just thinking out loud.)
Can't be communities made like bots? It would repost notes that match certain criteria similar to your second point and anyone could (un)follow, mention and zap it.