Some languages use multiple variants, often with different scripts, and use LanguageConverter to convert between them. For example, on Serbian Wikipedia, users can use either the Latin script or the Cyrillic script, with the interface translated separately, and the content transliterated automatically.
We should figure out how to make maps work well with this. We probably need to send a different language code to Kartotherian for Serbian depending on whether it's being viewed in Latin or Cyrillic. What we need to do here depends on how MediaWiki represents these things, and also on how OSM represents labels in these languages.