Nafi ibn Abd al-Rahman ibn Abi Nuaym taught in Medina through most of the eighth century, in the city where the Quran had been recited without a break since the Prophet's lifetime, and the reading that carries his name stands first among the seven that Ibn Mujahid set down in the early tenth century. Medina mattered to the reciters for a reason easy to state and easy to underrate.
The codex Uthman sent there was one of a small number of regional exemplars, and the recitation practised in the city was held to descend directly from the people who had learned the text by heart from the Prophet himself. Nafi is reported to have read to a large number of the Followers, the generation taught by the Companions, and to have made his own selection from what he heard rather than reproducing any one teacher. That is what a reading is in this discipline: not a private opinion about the text but a set of choices inside an inherited range, each choice traceable through named people. The sources describe him teaching for decades, long enough that his students belong to two different generations, and two of those students fixed the reading in the form it now has.
Qalun stayed in Medina and Warsh went home to Egypt. Between them they carried Nafi further than any reader except Asim. It is recited today from Morocco to the Sahel, which makes it the reading of a very large part of the Muslim world, and the one most likely to sound unfamiliar to an ear trained on a printed Cairo text.