Currently localed knows about the `LC_*` variables and the `LANG` variable but ignores `LANGUAGE`. LSB 4.0 describes the `LANGUAGE` variable: it is used, at least by GTK-based applications, to choose the language of the displayed messages. In my case, my `.profile` file sets LANG=it_IT.utf8 LANGUAGE=en_US:en because I prefer having an English interface but with European defaults (A4 paper, EUR as currency, Monday as first day of the week, etc.). The `LANGUAGE` variable is also set by the GNOME's language switching utility.
Hmm, what you are trying to do you can do without $LANGUAGE: LANG=it_IT.utf8 LC_MESSAGES=en_US
The GNOME i18n setup tool does not set $LANGUAGE.
Nonetheless if I have now update systemd to set support $LANGUAGE is well, even though I presume it's not going to be used by much.
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