I'm a righty, but i hold my pen weird too. I always wanted to learn to do it "right" so i got a lot of those grips you put on your pen with the indents where your fingers go, but it never stuck. I had a bump on my ring finger for a while, but now i think its pretty much a smooth callus if anything.
a girl who used to be my best friend is a leftie, and me, her, and another of our friends would be walking somewhere or something, and this girl would point to someone and go 'look! he's a lefty!' it always interested me that, maybe not just with handedness, if you do something "differently", you're more in tune with others who do it the same as you, or another different way. Of course, she doesnt call herself a leftie persay. she's a "leftie with righthanded tendencies" since she does a lot with her right hand. We always used to tease her cuz she always smeared when she wrote.