Found the relevant part of the post: How Keybase solves this problem: End-to-end encrypt all messages, but only "exploding messages" (coming soon) will have F

Found the relevant part of the post: 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.