In my case, the culprit appears to be my session dbus daemon, which has LANG=C and GDM_LANG=C in its environment.
Unfortunately I have no idea whatsoever where it gets the LANG envvar from. Help? -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org