This isn't really a habit that much, bit soemtimes (this really bugs me) I accidwntally (that wasn't on purpose!) replace an 'e' with a 'w' I hate when I do this and it is the most common spelling mistake I make in comments, and books. I type quite fast on my phone and I guess my thumb hits the 'w' instead of the 'e' most of the time...

I'm running out of ideas...