@Keegan suggested I come here. My user page causes me to have a list of languages I don't understand on Wikidata and the caption feature. I didn't even know my user page doubled as a configuration/preferences page!
Please ignore level 0 languages.
Update 18 January: a better solution would actually be to configure the languages you see in https://meta.wikimedia.org/wiki/Special:Preferences. Levels and babel boxes wouldn't matter anymore. It would also make more sense, because no user can be expected to guess this is how you configure which languages you can edit.
Update 20 January: ignore the title. This request is not Commons-specific. Whatever solution we come to, it should apply equally to Commons captions and Wikidata labels.