Personally I'm a supporter of the understanding that "women" are a political class, the boundaries…

Personally I'm a supporter of the understanding that "women" are a political class, the boundaries of which is structured around sex differences. I think that's undeniable - so much oppression of women occurs through physical issues like reproductive capacity.

The issue I have is with absolutism around the boundaries and borders, and the insistence that it is only by keeping these borders tightly defined that feminists can hope to achieve liberation. In fact I think the rise of trans people is the result of feminism's successes in eroding the power structure of Gender - in eroding the barriers between men and women and chipping away the idea of essential difference allowing trans people to be increasingly open about our previously very covert existence as a hidden minority of Gender Transgressors betraying the sex class we were born into to cross this mythical and socially policed boundary.

I don't think that upholding this boundary does anything useful for women, for liberation from patriarchy. The patriarchy is based on the exploitation rooted in the class system and travelling across its divides has been violently policed for centuries - if continuing this was going to liberate women it would have done many years earlier.

And yes, I think there are problems with the term "Gender Identity" because it's part of the confusingly overloaded way that "Gender" carries far too many meanings to be sure which one we're discussing at any time. I almost think "Sex Affinity" might be better - we experience a feeling of kinship, of self-sameness with a wider gendered group (or disaffinity with any such group), for whatever reason. But I think we could equally just keep Gender Identity language as we do understand collectively what it means (aside from charlatans who pretend they don't).