I realized that the notifications are being send in the language of the sender not the recipient. I am aware that changing this will require to store the not localized versions of the body and subject in the notification tables and then do a lang::util::localize when sending the notification, but maybe it is on purpose that the notifications are not send in the language of the recipients.
If I change this, would this require a formal process (as notifications I think is part of .LRN ?)