Having a central server is not necessary, but we have one anyway and we use it, especially if you have a permissions system. It lets us use the "Google wave" algorithm which vastly simplifies things.

https://svn.apache.org/repos/asf/incubator/wave/whitepapers/...

> This is not always easy in either case, and to do it right you might have to think very hard about things like "how to preserve position mappings," and other parts of editor state that are crucial to (say) plugins that manage locations of comment marks or presence cursors.

Maintaining text editor state is normal. Yes you do need to convert the OT messages into whatever diff format your editor requires (and back), but that's the standard glue code.

The nice thing about OT is that you can just feed the positions of marks into the OT algorithm to get the new positional value. Worst case, you just have the server send the server side position when sending the OT event and the client just displays the server side position.