I think I'd agree with you about the smile vs scowl (or at least less smiley). Part of it is that transgenders in either direction do what they can to fit the gender of choice, and consciously or not play out cultural stereotypes. I know for a fact that my mom was always telling my sister to smile and me to straighten my shoulders. Its socially programmed
Of course nobody has to feel obligated. I think in general I should smile more often, en femme or not. cheers