It works like that: spammers are going to operate using powerful servers with lots of computing resources and minimal energy constraints—that's the nature of their activity. In contrast, legitimate users often rely on smartphones or low-powered devices. This creates a fundamental problem for PoW as a spam mitigation strategy: there’s no viable threshold that can effectively hinder spammers without also significantly impairing regular users. Bitcoin is very different, as its use of PoW is fundamentally different: it’s a competitive system where miners race to solve a game in a winner-takes-all model. That schema does not make sense in a microblogging protocol like Nostr.