I am running my phone in my native language (not English), but my Xbox (therefore all my games incl Destiny) in English. Reason being that in my opinion the localisations have become worse and worse over the last 2 decades since I started gaming. As a consequence of the setup I am running the game in English and the app in German. It's inconvenient. So I think there should be an option to manually change/override the app language.