I guess I didn't realize it was really anything. I am right handed and although not as neat, write both print and cursive in mirror. It feels as natural as regular writing. It does, however, feel like I am writing left handed. A lot of times I have to be aware so that I don't write mirror.
I can do it with the left hand as well, but it is obvious that it is the non dominant hand. What I find interesting is that the letters that children reverse like d and b are the letters that may be reversed for me, or accurate I suppose, depending on how you look at it.