I feel this would probably be an issue when traveling to certain countries that force you to choose male or female when feeling out there entry records. And as you probs know, some countries are extremely closed minded in stuff like this. I wonder if this X would make it harder for some folks when traveling abroad.

Along the same thought, this could cause more problems than it's worth unless this becomes a more universally accepted way to treat the passport going forward. Imagine being held up in customs for 3 hours due to mismatched documents (ID & passport)

Gender non-conforming persons are still a small minority. I think in the vast majority of cases, gender will still be tied to appearance.

It’s not really about physical characteristics that match the letter as much as having another identity marker to differentiate people who may have the same name, and to track them across systems. We could theoretically give everyone a random letter of the alphabet and probably be just as good. We’ve had gender nonconformity for ages. In the Middle East, men without beards are feminine. In the 60s US, men started wearing their hair long like women. This is just an extension for that

Does your passport state sex or gender? I have two on hand and both state sex.

"if all things are special than nothing is special."