I think a comma between gentleman and scoundrel. Has a nice rhythm to it.

I think it's better without the comma, as it implies that you are a person of good breeding and a charming rogue, rather than a boor with a title.

Hmm. I like "Writer, Artist", but I like it mostly for the line length (anytime I see short lines that aren't contact info, I always feel like maybe it should have been put up with the line before it).

What about "Gentleman, Scoundrel, Gentleman Scoundrel"? Then there's no confusion, and you can still add the "Writer, Artist" part in front.

"I am GreyWeirdo on The Internet" seems... I don't have a good word, but it's the sort of thing I would expect to hear from a spinster aunt who figured out that she could get the same username on AOL and on MySpace, and doesn't fully realize that there's more to the Internet than AOL and MySpace. Perhaps "I am GreyWeirdo on most social networks"?

.... oooooor, you could take out ALL the commas, and let people judge for themselves whether there should be two or three of them. "Writer Artist Gentleman Scoundrel"