@Everyone wondering why if Link and/or the game is mirrored, EVERYTHING has to be:
It's impossible to mirror ONLY Link or to mirror ONLY the world for two reasons-
1) gameplay. Things like collision detection and the way Link's sprite interacts with objects in general are animated and oriented against the camera in extremely specific ways that only take the pre-set orientation in mind. A good way to explain this is to use Link's shield. If you try to block an enemy's attacks, the way it's animated and programmed is designed (usually) to "collide" with Link's shield. Now imagine that Link's shield is on the opposite side of his body. Now the game has to be programmed in such a way that when the game is played in lefty mode, it still looks like attacks bounce off Link's shield. This means either the enemies have to be programmed in an extremely complex way or the enemies have to be mirrored also.
2) cutscenes. All cutscenes are scripted with camera angles, choreography, etc. that are built specifically with the default orientations for both Link and the world in mind. Change one or the other and you have to change the cutscene. The only way to mirror one is to mirror both.
It's IMPOSSIBLE to include a lefty option without including a mirror mode for the game, and somehow I doubt Nintendo thinks they can get away with using the mirror mode solution again.