If there are many relays, clients are going to need to get better at making sure events actually get to the relays of the receiving user. A user could be on another relay you don't know about, and you could try to reply to a user thinking they will receive the message. right now there's no good way to know if a message will get to a user in a scenario where there are many relays, and that's no good.

We need a better solution for those situations. Right now if you're a group of friends you can just make sure to all join the rough set of overlapping relays, but there is no protocol-level mechanism that bridges theses relays, other than relay hints in notes and individuals manually mirroring notes from one to the other.

nostr is not consistent or even eventually consistent, so we need better client mechanisms to make that a better experience.

perhaps it's not an issue if there is a small set of large public hub relays that everyone can broadcast to...