In places such as Bukhara, the language encountered — still ostensibly a variation of Persian — would be near incomprehensible to someone with knowledge of “colloquial Persian.” The same goes for Afghanistan and even Iran itself. The formal Persian of the media is virtually identical across borders, while the spoken dialects vary tremendously on a city-by-city, village-by-village basis. [...]
This basic insight is taken for granted by scholars with years of experience studying Persian (by its various names) and living in Iran and Central Asia. But it is a language framework missing from most Persian textbooks and actively subordinated to an explicitly national way of understanding language dynamics in the region.
The language categories we are more or less stuck with are organized vertically by nation-state, which at once obscures the profound variation of local dialects (Mazandarani, Bukhari, Kabuli, and many others), while simultaneously implying deep differentiation by country that does not in fact exist, among Farsi, Dari and Tajik.