Welcome to Gaia! ::

My sister (who looks like me) told me "you can't go out in public like that! someone might think you're me!" (I was wearing a Nightwish top, black and white armwarmers and a floor-length black shirt.)

Really I haven't been insulted. At all. sweatdrop The odd "It wouldn't kill you to wear color" comments, but that's expected.

Of course this might have something to do with the fact that I go to a REALLY small school, everyone knows everyone. Also I don't wear my good clothing for school (mostly just plain black unadorned clothing).

I hardly go anywhere except friends houses and school. I don't really have a life, and I need a job. stressed

And of course my parents disapprove of the way I dress, and they have made that known. For the last 2 or so years now, any clothing that's black, I have to buy it myself. But that's just typical. I have it soft compared to pretty much everyone else.

Emotions are not an expression. They are simply feeling that you express through art. Not everyone expresses an emotion. So the OP is right, it expresses her feelings and artistic inclination. Self adornment plays no other role than as emotional expression.
So..you don't believe in ART obviosuly. Cuz last time I checked, we artists used art MATERIALS to express ourselves. I find such an assertion insulting to the entire art community. Yes, our appearnace is self expression. We put alot of hard work into presenting an image that we like, whether it be with make up, piercings, sewing, dying, tattooing etc.
I'm sure the lovely Black women who put their hearts and souls into their intricate hair designs would be a little angry with the assertion that their craft is not a form of artistic expression.
http://www.youtube.com/watch?v=ymwLbqYYAZo
That's insulting to ME personally as it's part of my culture.
I don't know, perhaps you live in a world devoid of visual arts. To me, the body is nothing but a canvas. Maybe that's something you just will NEVER understand. Think outside the box a little. Instead of playing the HTT role. Humans FEEL and they do feel insecure at times. DUH we're imperfect beings. A person who never doubts themselves is in fact not a human being. "Faith in the face of doubt, that alone makes us human".