Lightning network.

I only know who zaps me on nostr because people post to nostr that they zapped me.

I outright don't know who zaps me on SN (except if it's some specific amount thats unique to them) and SN only can figure out who is zapping whom based on the IP of the person visiting and the invoice it gave them, but visit SN via tor and its hard to say SN knows much at all.

With that all said, we can zap each other directly and who's to say we had a transaction at all? Later when we close channels people can say something happened at some point but exactly what remains unknown to people who have no need to know.