Catching up on my reading I finally read the piece by Mary Norris, long-time copy editor at The New Yorker, in that magazine's 90th anniversary issue, and learned that the comma was invented in Venice around 1500 by a printer named Aldo Manuzio.
I immediately wrote about this to my friend Luisella, who is a tour guide in Venice. She wrote back saying that she was currently writing an article about Manuzio.
