That LanguagePronouns array lives in the English Language kit, and you cannot have duplicates.
So I think the only way right now would be to copy the English kit into the external folder and edit the copy, which will override the built-in one. But that requires several workarounds for the moment, see Updating translations for Inform 10.1.0.
EDIT: I’ve been informed that replacing a symbol other than a routine is supposed to work. I haven’t tried it, though.
Include (-
! ==== ==== ==== ==== ==== ==== ==== ==== ==== ====
! Gender Options replacement for Language.i6t: Pronouns
! ==== ==== ==== ==== ==== ==== ==== ==== ==== ====
Array LanguagePronouns table
! word possible GNAs connected
! to follow: to:
! a i
! s p s p
! mfnmfnmfnmfn
'it' $$001000001000 NULL
'him' $$100000100000 NULL
'her' $$010000010000 NULL
'them' $$000111000111 NULL;
-) instead of "LanguagePronouns ".