Apparently I also printed this way, and Markus' old Brio trainset is proof that at least one of he or his sister printed backwards, as remeoR seems to be printed on some of the pieces... I wonder when our brains settle in on one way of perceiving the world. And if I just never correct her, will she continue this way? She also reads picture-books upside down, by preference. And sometimes she prints letters all on their sides, with the words heading vertically or horizontally.
Note that she appears to be printing upside down and backwards, but she's actually printing left to right, from her perspective, just upside down. So from her perspective it's just inverted letters going the right direction; from ours it's a perfect mirror-image.