If you were among the 40,000 fans at the Cincinnati Reds game against the Cardinals last month, you might have caught it between innings — a flash of red-and-beige jerseys on the Jumbotron, and three plain words arranged above them: Sign For Hoy. It was the kind of moment that reads as spontaneous but isn’t, the kind that requires someone, somewhere, to have been planning it for a very long time. Those fans had come from across the country.