Since we launched map internationalization earlier this week [1], a number of users have asked about the map language-fallback schemes and how communities can change their fallbacks (e.g., this exchange [2]).
I added a post today [3] to the Map Improvements project page that goes into detail about language fallbacks. It explains how to request a change and gives an example of why some less widely translated languages, at least, might want to consider adding to their fallbacks.
I’m sure there are many angles on this question we haven’t considered. If you have thoughts or questions, please share them on the project talk page [4]. We’re listening.