If you extend your name to something long, like say yaddle_the_unstoppable_sex_machine, it very often stretches out the margins of all the posts in the thread, and makes reading them more irritating.
It's supposed to break it up & bring it down to the next line to NOT stretch the margins (it does on my screen, anyways). Margining stretching (theoretically) only happens when there's a word that can't be broken up because there's no spaces (like a 300 character NOOOOOOOO!) or an image that's too wide to fit.
Are you using an older version of IE or Netscape or Opera? I'm not sure where the code parses, on the server or client sides.
(Of course, if you don't put any spaces in there, it can't break it up, but if anyone's done that, I haven't seen it.)