And I get where we're coming from, looking for in-universe precedent, and saying, "But hey, this character once said 'he or she', so we should abandon all else and go for the least succinct option here!"
However, here at Tardis Wiki, the rules of the English language -- and British English specifically -- take precedence over specific language usage in the DWU, except in very specific circumstances where British English has an alternative spelling as an option, as well.
- Also, this is all specifically mentioned in T:DOCTORS, so unless a community discussion is closed by an admin in favour of changing things, this pronoun usage is laid out in the Manual of Style.
- I'll explain in a minute that we've already ruled all this from past discussions, but it should be pointed out that it would be in violation of T:POINT to go about acting on your position here, contrary to T:DOCTORS, while this thread is open.
So if you're sat wondering why we're using singular they for a character with multiple genders, for a character of indeterminate gender, or for a character outside of the gender binary, it's because we're using English.
Alpha Centauri is not a he or a she, either, and even though some early sources had the Doctor using he/him pronouns, later sources opted for better neutral language.
Now, we've had this discussion before -- here and here -- and we ruled that:
- In general, use the pronouns given within a narrative. (This might be he/him, she/her, they/them, such as for Orr, and for Sgloomi Po, it's actually [ze]/hir.)
- If no clear set of pronouns is given, default to they/them.
- If stories conflict and give different pronouns, default to they/them, instead of flip-flopping based on the story cited. (This is the case with Alpha Centauri.)
We're in the "business" of presenting information from DWU narratives, truthfully and to-the-point, using our own language to best describe what is presented to us. And we have the Manual of Style to standardise the language we use across Tardis.
So, for a Time Lord who uses different pronouns at different points in time, it's they/them in general, and when referring to specific incarnations, use the pronouns given. It's "the Doctor and their TARDIS", the "Thirteenth Doctor and her TARDIS", and the "Second Doctor and his TARDIS".
"The Master killed his next incarnation, Missy", and "Missy was killed by her previous incarnation, who took their future into his own hands." "The Master usually regarded the Doctor as their enemy, but in one incarnation, Missy found herself befriending him."
If you think there might be some confusion, swap out a pronoun for a noun, or add the same pronoun earlier on for consistency, and you'll have better flow.