Development Discussion Board

For it does only affect right to left languages (Arabic, Persian), would it make better sense to put it in bidi.css, so that only boards that use it use the Tahoma font?

Well seems like a huge list of language iso-s ;)

I'd go the way of https://developer.mozilla.org/en/Localization_and_Plurals#List_of_Plural_Rules
So we basically implement the rules (mostly the same as in symfony) but use a int key which rule to take.
Language package authors than simply specify ...

Yes, same thing happens in Arabic also.
To quote the same example you used, in singular word "1 elephant" we would say: "فيل"
For 2 numbers, we say: "فيلين"
We begin to use numbers beginning from 3, and again from numbers 3 to 10 we say: "3 أفيال" or "7 أفيال"
For more than 10 numbers we say: "11 ...