Well I'm all for adding the artificial shading on certian characters, so long as it's accurate and consistant. For instance, if your going to add a black patch on Batman's mask, remember to blacken his trunks and the interior of his cape as well. The artificial shading doesn't work in just a single area, especially when it's shown against a very bright color. So for the sake of consistantcy and accuracy, I think it's a better idea to add the shading in places where it looks more aesthetically pleasing.
Good points. Personally I'd prefer Batman to be all blue, so I plan on removing the black from the mask. It will probably work with denatured alcohol on a rag.