Since all answers to the previous FAQ have been deleted and this concern isn't addressed in the new FAQ I guess I'll ask again:
How do you think this is going to work for regular (Stack Overflow) users?
Regular users don't read Codes of Conduct, FAQs or other guidelines. We know this because thousands of garbage questions come in every day.
And for 99% of the users, 99% percent of the time, on 99% percent of posts gender pronouns are completely irrelevant. So you can't rely on users stumbling upon them via normal interaction with the site.
This means the first interaction regular users are going to have with neopronouns will probably be an unpleasant one. You might say that doesn't matter since 99% of the time this won't come up. But keep in mind that 0.01% of first time Stack Overflow users is still a lot of people. Every day.
Also keep in mind that in most parts of the world (like mine) gender pronouns(neo-)pronouns are not a thing. We don't learn about them in English class, we don't encounter them when consuming media, we don't hear them in every-day life. This means for most of your users, the Code of Conduct holds surprises.
If your Code of Conduct includes surprises for at least half of your users, you are going to have a bad time.
To me it seems in your quest for inclusiveness, you just forgot about everybody who doesn't speak English natively.
Do you have any plans to make this easier for non-native speakers, other than canned reassurances (like U3)?