Gnome Documentation Style Guide
The Gnome Documentation Style Guide includes this statement:
"Avoid sexist language
"Pronoun constructions such as his/her or s/he do not exist. There is no
need to identify gender in your instructions."
Interestingly enough, this document acknowledges that:
"Many of these guidelines are only applicable to English-language usage,
see the American Heritage Dictionary and the Chicago Manual of Style."
The Gnome document appears to be the sort of thing that might provide a
useful baseline for evolving a Debian Style Guide.