But text is already symmetrical along the z axis, so it works.

Say your hands were 2d, so the backs looked the same as the palms. Now hold your hands so that you're looking at the palms and the fingers are pointing up. Rotate your left hand 180° along the y axis, and it would look like your right.

I misinterpreted the comment to mean a 2D reflection is a 3D rotation, in general. Thanks for pointing out the comment was about this specific case.