Idk, there’s probably a use case but I don’t see it with a social network the way you’re describing. Makes no sense to repost old notes, the whole point is the historical context and the conversations that happen/ed on them, need to be able to re-up a note’s PoW to keep it on relays, thus spam would be auto deleted, not new spam, but historical, while real people who care about their notes can dedicate some PoW to maintain them