Why is "your language" even in matchmaking parameters?

It doesn't ever change from "your language" so why is it even there? And what language does it even use? My language is german yet I play the game in english.

And more importantly, no one talks anyway, and I don't even think you can talk to your enemies, so why does the matchmaking find you opponents that are 100 levels above you instead of finding similary skilled opponents in other languages?