Yes, this would be a nice feature. No idea how complicated it is to implement. Because a note could have conflicts on several devices.
So how would you name them? Maybe we could use the client id somehow.
Also, how do we link the conflicting notes? (Otherwise how do you know which notes are conflicting? Just by the name. Well, it could be enough.)
Hmm, maybe name it like Note title (Conflict: <clientid>)