The Couch is a role-play item, comparable to the Armchair and Loveseat. It is possibly the heaviest item in the game. This couch is just for resting or an AFK (Away from keyboard) spot or for plain decoration.
Non-whitelisted players will be teleported to their spawn point if they attempt to sit on any chair repeatedly.(since the new update it does not do that now; non-whitelisted players will be able to sit on a chair belonging to any player.)