"Leonardo", not "da Vinci"

From a fine Nordlinger Impromptus today:

The mistake of referring to Leonardo as "da Vinci" is so entrenched, I'm afraid it's uncorrectable. I have had to fight with editors about this: You say "Leonardo," and they want to say "da Vinci," thinking it's his last name — thinking it's the same as saying "Reynolds." They think that, when you say "Leonardo," you're saying the equivalent of "Joshua." Actually, to say "da Vinci" is to say "of Orange," instead of "William."
...
Look, there's nothing to be embarrassed about. You have to learn at some point. I remember when I learned — when I was a college student in Italy. An art-history teacher asked whether I was interested in a particular artist, and I answered, "da Vinci." He looked puzzled for a moment. Then recognition crossed his face, and he said, "Ah! Leonardo."