China [1] and Brazil [2] feature strongly non-English developer communities. Regardless, keying such features to a language is just painfully ignorant. On a closer look though, it appears that beside the developer edition having the setting, the unbranded version will only be released for en-us.

ESR has some bits about "Learn English if you want to code" - but politics of it aside, this isn't even about coding. This is about using a plugin that someone has not signed (like, for instance, RES for Chrome which for the longest time did not have a Store entry iirc).

1. http://segmentfault.com/

2. http://pt.stackoverflow.com/