I've noticed that there is no smaller or larger tags for characters of ambiguous gender. Would it be justified to create these tags for the purpose of comprehensive tagging of size_difference posts, or is this too small a case to account for?

Would anyone actually search for those? If not, there's no reason to tag them.
Unlike the other gender tags, ambiguous_gender exists mainly for the tagging and sorting purposes. And I can't think of any tagging projects where those would be useful, since wildcards can't be used to exclude posts (example: size_difference -smaller_* just searches for 'size_difference').

Qmannn said:
I have seen some people who have a preference for those of an ambiguous gender

Good enough reason to tag them, then.
I don't remember ever seeing anyone mention that they specifically search for ambiguous, but it sounds plausible enough.

Sounds good, matches with the other [size]_[gender] pairs

-

Genjar said:
Good enough reason to tag them, then.
I don't remember ever seeing anyone mention that they specifically search for ambiguous, but it sounds plausible enough.

It's a good way to search for gendered posts too, at least where size differences are concerned