Wikimedia Bugzilla is closed!

I'd like to have the option to let the browser and/or the user decide what
language the interface has.
The (logged in) user could set it in his preferences and override the default.
The browser submits the desired language in HTTP_ACCEPT_LANGUAGE
So, the options could look like
InterfaceLanguageUser=TRUE
InterfaceLanguageBrowser=TRUE

Priorities: User, Browser, Default

I agree that it is not useful for all Wikis, as most of them are bound to a
certain language. But some (like mine :) may contain content in different
languages and be read by users from different countries.