Being "post-identity" means that a person is past the point of gender identity. (He or she does not identify with the fact that he or she is a he or a she)
This means that a person does not comprehend his or her genitals or amount of X or Y chromosomes that a person may have.
This is a commonly used term by Gay and Lesbian activists that describes the superior mindset of the activists over the majority of society. Being post-identity not only makes you a more understanding person, but it increases your intelligence and charm around fellow liberal minded individuals.
Bro 2: Umm... shes straight but she says I'm not post identity enough
Bro 1: No worries bro, just tell her you don't know the difference between dick and pussy !