I think I'm going to stop saying "on Nostr" and replace it with "in my network (as in "are there any good notes on Nostr?", "Is there censorship on Nostr?", etc)
There is no single Nostr network, but rather a patchwork of voluntary islands. Each npub who posts to relays has a personal network in that moment.
Who or what is "on Nostr" is different depending on where, when and how you exist in that graph. Talking in terms of "on Nostr" is just a guarantee to have constant disagreements about our subjective experiences in our region of the graph.
