Hi all!
I believe that for anonymous users, the interface language should be chosen based on their Accept-Language. I think the required code is simple, see the attached diff for a basic sketch that seems to work (really only basic, some issues are ignored, e.g. when a new user is created, his default preferred language should be set to Accept-Language, too).
There are some further issues that should be considered -- e.g. what about Main_Page/Hauptseite/...? What to do with a user preferring some language not supported on the wiki? (Should there be some local setting with a list of supported languages?) Etc.
But I would like to know -- what do you think about the idea? (My initial thought was about the Commons -- users from many Wikipedias go there, only to find that, seemingly, the site is English-only. But their language is just a few clicks away; unfortunately, the clicks have to go through the English interface.)
-- [[ :cs:User:Mormegil | Petr Kadlec ]]