The server doesn't (persistently) keep track of every client's selection (or its best guess of those selections based on translation). The clients do do this, so every client knows every other client's selection. However, when a new client joins, it only receives one client's selection from the server (specifically, the selection of the client that most recently submitted a change) , which looks a bit weird. We could fix this by replicating the client's selection translation logic on the server side, which would only be used to ship a blob of all clients' selections to new clients when they join.