I'm commenting on your answer because you got the "right" answer first. This is what I was going to say: My explanation is that the reason a mirror appears to

I'm commenting on your answer because you got the "right" answer first. This is what I was going to say: My explanation is that the reason a mirror appears to reflect text (or anything else) horizontally rather than vertically is because, whether physically or in our mind's eye, we conduct the comparison by rotating our point of view around a vertical axis. If instead you adjust your point of view by rotating about a horizontal axis (e.g., compare what the UCLA on your sweatshirt looks like in your bathroom mirror to what it looks like looking down at your own chest), you find that things are unchanged left-to-right but upside-down vertically.