This is a good question and I think it's the perception that the person you see as a reflection is actually a clone turned around to face you. When you raise yo

This is a good question and I think it's the perception that the person you see as a reflection is actually a clone turned around to face you. When you raise your left hand, your "clone" (if it is a clone) raises their right hand. If you imagine stepping through the mirror and turning around to stand next to your reflection you really will be reversed laterally compared to your reflection-twin.