I have thunderbird that speak italian (correctly) but lightning speaks english Reproducible: Always
Yep. That's because mozilla's langpacks only include localizations for core thunderbird, not extensions. thunderbird-38.1.0 now grabs langpacks for lightning and shoehorns them into place, same as was done for 31.x and previous. This should work regardless of whether USE="lightning" is set or not, btw, so you can continue to leave the flag off if that is preferred. Note that with the use flag off, emerging thunderbird-38.1.0 might not actually upgrade the lightning extension in your profile. However, the update that is available via addons.mozilla.org should install all locales for the calendar and your thunderbird installation should offer to update those. If it doesn't do that automatically try checking for updates by hand via the Addon Manager.
