A note on flipped shots from a film editor's perspective:

99.9% of the time, when you see a flipped shot, it's to create an eyeline match when the actor was looking the wrong way, or when a shot doesn't exist where the actor is looking the direction they needed to be looking, so the frame is flipped. This is far more common than most people realize, and flipped shots usually go by very quickly. The theory is that it's easier to notice someone looking in the wrong direction than to notice a flipped shot (which is, usually, true).