Since multiple rooms have been recently added for dueling, players now have to include the number of a duel room and, optionally, a dueling player's ID when they want to watch a duel. However, when a player types a dueling player's ID but not the number of the room (e.g. /watchduel 16), a message is displayed by the server in the chat box saying that that it is an "unknown command". It can lead many people to believe that they have mistyped the /watchduel command and cause confusion, so I think it should be fixed.
Note: This only happens when the ID of a designated dueling player is a number higher than the number of rooms and zero.