This is an issue that has much concerned me. I had suffered from a small crisis of conscience when I changed how I dressed to avoid persecution/ possible expulsion after Columbine. I didn't think that was a choice I should have been forced to make, though at the same time, I wasn't willing to get thrown out of school over clothes.

I, for one, believe that it is just as valid an expression of Self as the above examples of people who don't have a choice over their appearance.
One could argue that the subcultural "dress code" has as much to do with maintaining solidarity with their group as an expression of self. The nuances of goth dress/ musical taste/ personality don't come together entirely naturally. People that look the part, but don't listen to the right music or vice versa tend to feel pressure to accept more acceptible genre alternatives. I haven't been able to decide whether that changes the validity of self-expression via appearance.

More thoughts possibly forthcoming.