I wish I was reading oldnewthing back in 2003.
That entry does explain the weird phrasing I see all around the UI (the most common - "X items selected" in Slovenian is translated as "This number of items is selected: X" - and it sounds much worse in Slovenian). Such phrasing is really unusual in Slovenian, and stands out, which is why I was wondering if the support for plural forms can be added in a future version of Windows (I've also seen places where "X things" was used [in Slovenian], which was not the right plural form for X). A certain popular open-source localization framework has a working solution.
BTW, that article mentions that Slovenian has dual - this is true, but we actually use 4 different forms depending on the number of items.