telling trans folks that their gender is a performance or costume is incredibly disgusting when you consider that cis folks are never told the same thing and don't have anywhere near as complex a relationship with their own gender.
don't make shit extra complicated for trans folks. we've got enough invalidation coming our way. even if you're also trans and like to consider yourself performing/wearing a costume, that's you, not me.
It's stuff that society feed to us constantly. Everyone *learns* what are the gender norms of the society they live in and conforms or resists to them, whether it's by comfort, alienation, choice or necessity.