When I was finishing the translations, I found something important.
Let's say a company uses system with multiple languages; but system language is set to English, since it is the common language that everyone knows in the company.
But staff who knows X language decided to use system in X. But when answers a ticket or do any action, as far as I see, the ticket history is saved in the X language, not in the common language. And this might cause some problems when it comes to figure out a dispute or something like that.
And I think logs work like this as well.
Also this applies to the visitors who changed their language as well, when history is saved, it is saved in the visitor's language.
This also applies to the mail subjects since system feeds them from language files. So if a staff uses the system in X language, no matter which language the visitor uses; system sends an email subjects in X language It might be hard to send mails according to the visitor selections but at least using the common language would be nice
(Opposite also works, if staff uses in English but Visitor uses in X, when visitor adds a reply, mail subjects sent to staff is in X)
I couldn't test the mail bodies since I haven't translated them yet but I assume this also occurs in mail bodies.