The idea that binary gender is a "western concept" is a comfortable myth, kind of like "Things were so much better back in the day" or "People only disagree with me because they're ignorant".

What cultures out there have more than two genders, and the extra genders are not some sort of edge case?

: I appreciate your words and kindness, and I know you mean well, but there's a
: few terminology bits I have to clear up. Sexual orientation refers to a
: person's attraction to a particular, multiple, or all gender identities,
: or none. What you're referencing for me is the aforementioned gender
: identity that exists within all of us in a variety of ways, both cisgender
: or transgender, and binary or non-binary.

Would "Gender identity" be an acceptable shorthand term?

: Because of this, I was in fact
: born with a female's brain and a slightly altered male's physiology.

XXY?

: Felicia Sanderson was the first openly lesbian character in our universe
: and no problems arose in the story from merely her sexual orientation,
: just her actions that have resulted from it.

There's a trope where gays and lesbians have to die by the end of a story. Tobias Buckell was initially hesitant to write Felicia's death because he didn't want to play into that trope. Eventually he decided to go ahead, because her death as a character made the story better.

: As if no understanding of mental and physical health concepts and terminology
: has ever evolved over time. I trust the language used by doctors for
: medical science, experts in the field of gender and sexual studies, and
: those with personal experiences over that of a fiction writer who's never
: researched or faced gender issues for themselves.

Words have meanings, and if you can define those meanings, you've won half the battle. You see it all the time with words like "Poverty" or "Terrorism" or "Assault weapon". If you have a dog in the fight, you care very much what those terms mean.

Mr. Correia couldn't care less about the proper terms for gender issues. He's pissed off at the subset of science fiction fandom who insist that science fiction must serve a cause. Ask him about clips versus magazines or what exactly an assault rifle is, and he could probably talk your head off.

: So not only is the author informing his audience that acknowledging and
: including persons of non-binary gender identities is futile practice, but
: that they can't or shouldn't be respectfully included in a simple list.

Is there ANY simple list of non-binary pronouns?

Correia's point is simple: Write to entertain first, then you can preach.
Look at it this way: Nobody reads Ayn Rand's books unless they agree with her. She wrote primarily to proselytize.

Contrast "The Left Hand of Darkness". It hasn't fallen into obscurity, and it hasn't survived for decades because it became a movement's bible. It had an interesting tale to tell, and Le Guin didn't write it atop a soapbox.

Alex MacFarlane said, and I quote, "I want to never again read entire anthologies of SF stories or large-cast novels where every character is binary-gendered." That is checklist-reading. That is judging fiction not on whether it is fun to read or if it explores its premise in a fascinating way, but whether it panders to your favorite causes.

And hey, this is science fiction. We have Heinlein, we have Piers Anthony, we have Robert Reed, and dozens of other authors who tackle gender subjects on their way to telling a good story. There is no dearth of books on the subject in written science fiction, though there may be a shortage of well-written books.

: Cis is a Latin term translating loosely to "on the same side." When
: referring to a "cisgender" individual, cis male in this case, it
: acknowledges someone who's original physical characteristics matches their
: gender identity.

Yes, I know that one. Would have had a problem with 'gendernormative' for the five seconds it took me to open up Dictionary.com.

Now, would you kindly explain to me why someone would use "Cismale" as an insult? It's like calling someone a "Transwoman" or "Black male". Not all that insulting.