re: Hagia Sophia and Istanbul needs to be called Constantinople

And also realize that Istanbul is a Turkish translation for the Greek popular name for the city, Stambuli or Stamboul.

Had the city been called Constantinople by the people who lived there, in a colloquial sense (as the official name was still Kostantiniyye into the 19th century), I don't think the Turks would have changed the name. Or without Turkish nationalistic fervor.