Cody on Nostr: You’re right, this is indeed a problem. My current solution is relatively simple: ...

You’re right, this is indeed a problem. My current solution is relatively simple: when a user rotates their encryption key, they don’t immediately discard the old key. They keep it around for a period of time so they can still decrypt messages that were encrypted with the old key by senders who haven’t received the latest key announcement yet and are still encrypting messages with the old key.