Siebrand Mazeland, 10/02/2017 08:48:
TLDR: if browsing a map for French wiki, and a city only has a Russian and Chinese name, which one should be shown? Should the city name have different rules from a store or a street name? ...
Hard questions, but let me remind that CLDR has data on the script and usage level of languages: http://www.unicode.org/cldr/charts/latest/supplemental/language_territory_information.html (used by us mostly for https://www.mediawiki.org/wiki/ULS/FAQ#language-territory ).
So in your example, if I were visiting the French article from Réunion, and CLDR said that Chinese is spoken there ten times as much as Russian (I'm inventing), this would be a factor to consider.
Nemo