They don't, and I think they argue it's a security feature. It is, at least, intentionally designed that way, for better or worse. You can get per-conversatio

They don't, and I think they argue it's a security feature. It is, at least, intentionally designed that way, for better or worse. You can get per-conversation sync by joining multiple clients to the conversation. It's one of those things where you'd probably want to be less secure and always sync to all devices.