Summary:
It isn't immediately obvious what the description language selector that is newly implemented in ShareActivity does, because it's blank by default. And even after explicitly selecting a language, it remains blank.
IMO, it would be a good idea to have a language displayed by default (perhaps the phone language?). The selected language also needs to be displayed. After the user selects a language once, maybe we should also save it and use it for the next upload?
Device and Android version:
API 24, Nexus S emulator
Commons app version:
Current master, prodDebug
Screen-shots:

Would you like to work on the issue?
Preferably not.