While going through some config files for TWN, I noticed that there are many messages that are excluded from various validators – many more than there should be. Many messages are excluded from PLURAL or GENDER validation. When GENDER support, especially, was added to MediaWiki, a lot of translators would complain that their language didn't have gender differences, and so they shouldn't have to use {{GENDER:}} in certain messages at all. With time, however, the convention has developed that even in languages that don't need that distinction, we still translate things as {{GENDER:$1|something}} with only one parameter that is used for any gender.
A lot of messages were added to validation exclusion in the start, but I don't think that's necessary any more. Removing them from those lists would simplify maintenance overhead a bit.