I'm thinking about this in the context of an eventually consistent CRDT or something. In that case, you need to handle the use case of a client going offline (eg the person is on holiday) and they make changes but aren't online for 2 weeks.

If a peer isn't emitting changes, I don't see how you can safely merge their keyspace - since they might still be using that keyspace, but be offline, and you can't know.