Waluigi on Nostr: Only users with time and, most importantly, the machinery and know-how will be able ...

Only users with time and, most importantly, the machinery and know-how will be able to access such pow-limited relays. I don’t think you will have spam problems as the number of users in these relays will be quite small in the first place (having in mind the ‘normie’ population). But again, relays are free to decide who’s allowed to use their services anyway; they can whitelist, blacklist, charge usage fees and so on