Warning: Personal ramblings
[spoiler]I think V was Neutral with Evil tendencies all along. By comic standards, hitting on the good/evil issue of D&D makes for a great arc, and V's genocide does make for a believable D&D transition on that axis. So it seems Rich may have put some thought into increasing his readership. As for the robes/fangs/eyes, etc, as we all say "fluff is mutable" It's likely just cosmetic side effects of the deal with the devils that V made. Just as the spirits have no control over V, neither do the effects. But it's much easier to act out your evil side when you have encouragement and backing.[/spoiler]