Admins are necessarily English-speaking so there is no need for localizing admin-only pages. It can be implemented by replacing l where appropriate with l_admin that gets not extracted for generating POT files. This will remove a useless burden from translators.

Even though current admins are not really using anything but English, it seems safer to not do that for admin-only messages in more general pages, so as to avoid mix of locales. It would probably not be a huge gain in number of messages anyway.