The answer is in the question. You ask:

My last name isn't "D'Foy", or "Defoy", or any of the other myriad variations. Given the inability of too many people to handle my name correctly (and it seems so simple), I set out the rules. As people continued to mogrify it, I refined the rules until I got to simply brian d foy (see, for instance, my use.Perl post about the summer of 1996). You don't have to worry about capitalization at all, now, and you only have to use letters.

The more interesting question is why you think that's strange, given that you aren't using your own name. I use my name just about everywhere (that lets me) instead of a "screen name", and yet I'm the one who's made the odd choice. :)

When I started writing, I had to pick a form of my name that I would always use. This is especially important in the scientific literature so that people can find everything else you've written and all of the indices and reverse citations work out the right way.

Besides that, I'm the only one with my name who writes it like I do. I'm not the microbiologist Brian D. Foy, or the other one who goes to my dentist (although we're 12 years apart).

Why not ask chromatic why he does his name that way? He doesn't even have a good rationalization for his :), as he says when we were both asked that question at our book signings at the Portland Powells (which Chris Dawson recorded for a podcast).

You might also ask bel hooks or k.d. lang, but don't ask E.E. Cummings, whose name only appeared in lowercase because the publisher mangled it (see, for instance Norman Friedman's comments on his struggle with the publisher of his book on E.E. Cummings).