Oh, I think with screen names, if the original person didn't capitalize the first letter, then the name should stay uncapitalized(it's a grammatical error, but it helps identify the person, because there could be a marioguy and a Marioguy-two different people).
Like with me, jon, I perfer people to use a lower-case 'j' instead of a capital 'J'. That's the way I see it.