plor on Nostr: We have the tools with proof of work to mitigate the worst of spam. There is already ...

We have the tools with proof of work to mitigate the worst of spam. There is already a NIP to add PoW to notes, but that makes UX for normal use quite degraded. But what if we only had to do it occasionally? Let's say my profile contains a reference to a note on which I included PoW. Clients then could filter out users by which have shown a certain level of PoW, which if set high enough would make these spam attacks unfeasible.