I was asked this question today. My take on this is that we can only accept posting in other languages than English if we have at least one moderator that understands the language. Then, we should probably have special categories for each of the languages so that people can easily “mute” the ones that they don’t understand. (It would then be up to the moderators / users to decide if this category should have sub-categories or not.)
We can easily have moderators for French, Spanish, Italian… On the other hand, I know that there exists a significant Japanese Coq user community but I don’t personally know any member of this community, so opening such a category would depend on whether some Japanese-speaking Coq users are volunteering to become moderators. Same for Chinese, Brazilian / Portuguese, Russian, etc.
Anyway, that was just food for thought. What is your take on this?