Hi Emperyan. To tell the truth, I don't exactly know why it is not translatable yet. I suppose that this is the extension UniversalLanguageSelector. It is still marked as experimental. It has been already enabled on tranlatewiki.net but it seems that it is not available for translation yet.
Development on this extension is onging. It will be available when it's in a stage where it can be translated. At the moment, we are still hard at work getting the multilanguage fuzzy search and design implemented properly, and getting the performance at an acceptable level.
It should be fully usable, and i18n is missing in the "world part areas", but those are mostly visual and don't provide too much functionality.