Never, because many of us understand what's on the outside is a direct reflection of what is on the inside.
You may be aquainted with some 'illustrated' folk who are just spiffy, but your conclusions on character make as much sense as assuming a random kid doesn't like hip hop music because you know some who like classical.
Exactly. If you see someone walking around with a "White Power" tatoo, you can be pretty sure that that person is not worth talking to. If someone looks like they just barely survived an explosion at a pin factory, one can assume that the person is into pain and likes to make an exhibit of himself. Our hedonistic culture has gone off the deep end -- now people are seeking pain because they can't feel anything else.