You were not exchanging with me and I'm sure that's not what you meant, but gay and straight are genders now?
I'm not sure how you envision a character available to both men and women that is also gays and straight all at the same time for both genders.
Also, from a certain perspective, Liara can not be considered a lesbian/straight romance. She is seen as female by human standard because she get to play the mother (if she wants) and have effeminate/feminine traits, but for her species she might not be considered "female".
Saying all that, I would very like it to have a "main" companions that was gay or lesbian (doesn't even need to be romance-able in my case).
If you actually read the post, you'll see that it's actually clarifying a point made by Iananmus. Iananmus states that Liara is available to "both genders", but that doesn't actually make Mass Effect "fair" at all. Liara is clearly female, so all that means is that lesbians were thrown a bone while gay men still got nothing.
It's not at all implying that "gay" and "straight" are genders.
Liara is absolutely female, as are all Asari. They use feminine pronouns, their titles are based in human conceptions of womanhood. BioWare wasn't even trying to make them seem anything other than female. It's really, really obvious.
Even if Asari didn't consider themselves female (but they do, because they use feminine signifiers to refer to each other all the time), it wouldn't matter, because BioWare still chose to present them as females.