Easy way to consider it, when you look at another human being, you innately understand that their right is your left, so you're rotating your perception of thei

Easy way to consider it, when you look at another human being, you innately understand that their right is your left, so you're rotating your perception of their directions around the vertical axis. The mirror isn't actually flipping anything, the top reflects back from the top, the right reflects back from the right. The "flip" is your brain treating them as a person rotated 180°, not the front of a person as if viewed from behind