How about basic hygiene? Is that a no-no, too? "She is clean and doesn't smell. Must be covering for her incompetence." /s

I feel perfectly comfortable working in a T, jeans and sandals, and I pretty much wore a shalvar-jaaf (Kurdish pants) my entire graduate years, but if I am to meet anyone initially in a professional context I will wear a suite (fully aware of the reactionary views of the sub-set that apparently is so focused on surface matters that they would ignore technical competence and make decisions based on the fact that one wore a suite to, say, an interview.)