I like Nostr because it is designed delightfully simple. I think it already solved most of technical problems (one of remaining ones are key rotation, but it is

I like Nostr because it is designed delightfully simple. I think it already solved most of technical problems (one of remaining ones are key rotation, but it is actively worked upon), and what it needs is solution of social ones (i.e. marketing). As for federation: first of all, one of basic ideas of Nostr is that a note is published on several relays at once. It adds robustness to the system - one recent analysis shows that on average, one note is published on several tens of relays. Relays do not talk to one other directly per Nostr protocol, so after the publication, notes do not propagate between relays by themselves - but a specialized client can replicate notes from one relay to another. I do not know how often it is done in practice, but it is trivially easy to implement.