I use Xfce with LANG=hu_HU, and have plenty of desktop files which have a
Name[hu], Comment[hu] or similar localized fields. Still, xfce4-appfinder
always displays the value of the English field and always uses that field
when finding an application.

Whenever a desktop file has some field translated to the current locale,
that one should be taken to account instead of the default (fallback) English
name or comment. Also, slight differences (such as the locale is hu_HU while
the desktop files have simply [hu]) should be tolerated.