It turns out that I started signing my notes ".B ekiM" on an online service I started using back in 1986 or 1987 or so. It just stuck.
It's easy for me to type. I'd suppose that's because I have had plenty of practice. It's funny that one of the reasons I stuck with it was because "Blaszczak" is such an awkward name, but lots of people write to me and say that it took them a couple of years to realize that ".B ekiM" is nothing more than "Mike B." backwards.