I wonder how that would work with key rotation. Those chat services do a lot of key management for you during a conversation, while Keybase is more focused on long-lived keys.
End-to-end encrypt all messages,
but only "exploding messages" (coming soon) will have FS.
Therefore, your history will survive, encrypted, except for the messages you choose.
How Keybase solves this problem:
End-to-end encrypt all messages, but only "exploding messages" (coming soon) will have FS. Therefore, your history will survive, encrypted, except for the messages you choose.