I've seen a lot of stuff about Twitter's language inference and I've got to say that the secondary languages can't be based on behavior.pic.twitter.com/g9WCua0Fcx
You can add location information to your Tweets, such as your city or precise location, from the web and via third-party applications. You always have the option to delete your Tweet location history. Learn more
I meant, maybe that's one of the factors in the mix? e.g. LinkedIn uses your language preferences as an input to your connections graph.
Twitter may be over capacity or experiencing a momentary hiccup. Try again or visit Twitter Status for more information.