Is there a way to use Nostr as a coordinator for payjoin or coinjoin? Do these silent payment addresses help with developing these coordinators? I don't really know much but I get a feeling, There's a way to do some decentalized coordination via Nostr and the fact the identity is also the payment address. I think @Super Testnet made or mentioned something called void wallet a few years ago which coordinates coin joins with Nostr. 
GitHub
GitHub - brilliancebitcoin/void: A work-in-progress bitcoin wallet that only sends and receives coinjoins
A work-in-progress bitcoin wallet that only sends and receives coinjoins - brilliancebitcoin/void