Plural changes in many languages
As you can see, those languages are mentioned in this message further down, as something different changed for them: Russian, languages having Russian as fallback, Serbian, Ukrainian and Belarusian.
Yeah, I figured it out in a private chat with Amir. From the prepending obscure notifications of changes that I've recieved, I thought Belarusian would suffer form order changes as well, but the MediaWiki implementation is the same as CLDR rules, so it's going well for me. :)