I never understood Saylor's 'orange check' idea. Pay some money to be "verified", but after that what's the cost to spam? It might work for Twitter because you can get banned and lose upside of verification, but how would that work on Nostr?
PoW at least provides a cost to every post. I won't mind 5 seconds of my phone's battery life being spent to send the occasional note, but spamming tens of millions of times occurs a cost that quickly exceeds any earnings from the grift.
IMO, PoW is the simplest answer.