*Sigh*

But then, it's not much different to what they (apparently) do in Hong Kong. Hong Kong ID card (which is compulsory to obtain & carry) contain a field for gender, which they are willing to change. However, a B get added postfixed to the ID card's number if the DOB, gender or place of birth is different to the person's birth certificate. Since the other two can't be changed, they might as well have transgender written in large characters.

Hong Kong passport have a page which list one's ID card number, so I'm guessing that applies to the passport as well, though the number is not on the photo page.