Hi William

It is possible to customise the language pack 

1. Select Site Admin > Language > Language customistaion
   
2. Select the English (or other)
   
3. Select All of the components
4. Type in " his " without quotes in Only Strings containing
5. Press Show strings button
6. Type in the Local customisation with generic pronoun eg their
7. Select Save 

There are actually six cases where " his " is used in the version 9 site - I will file a ticket to get these changed in the standard English language pack.