One of my most treasured quotes about femininity (as opposed to being a woman) is this from Barbara Kingsolver, from Prodigal Summer:
“Feminine” was a test like some witch trial she was pre-ordained to fail.
It encapsulates, perfectly, the way in which the concept of femininity as a performance is also one of competition and measurement. Genderqueer behaviour may subvert femininity but it is still a concept, still a performance to be measured and judged. However fun or inconsequential the results are, the underlying assumption is one where the performance of femininity has a measurable objective to it.
That the feminine is real. And for the most part, a visual performance codified sexually.
Rule 63 cosplay often reinforces this notion. No matter the original, the Rule 63 version that is shared and re-shared and exposed positively to the world is attractive in an expected way, without challenging the mainstream notions of attractiveness. In fanfic it is often a very concious and vocalised rejection of the feminine, of those coded feminine roles and interests, with that very clear conceptual underpinning of ‘masculine is better’.
This acceptance of the underlying ‘rules’ of femininity, whether reinforcing them or rejecting them, obeys and legitimises them.