I found out about 3 years ago that I write better backwards than forwards (like Leonardo). It is partly mechanical (I'm left handed) but partly something to do with how I process information. My forwards handwriting gets really bad -- I find my backwards handwriting easier to read. I have no problem keeping my letters going in the right direction when I'm writing backwards -- I'm better at it than when writing forwards -- except for numbers.
Numbers are, for whatever reason, very hard to write in the right direction for me (honestly, forwards too), though reasoning about calculus and graphs is far easier backwards.
Anyway, I'm still trying to figure that out. I think it is that our minds are coded to pick out language, so that pattern matching isn't so hard, but less capable of decoding numbers and reasoning about them.
At least for me.