Hey, this is kewl. If anyone mistypes my nick as mj (lowercase) you automatically get redirected to the proper (upper case) link. This is at the server level, I didn't create an account for the lowercase spelling with nothing but a JS redirect or something. Thanks raph.
As it turns out, this works with any nick with upper case characters; when you create an account, an all lowercase alias is created to avoid name collisions. Apparently some parts of Advogato are case-sensitive while others are not. Lucky for me =).