Kelly Ellen Mulrow and Kevin Matthew Quinn like clockwork recitedthe opening lines of the Latin textbook “Ecce Romani I” during their first date in May 2017 at Ampersand, a cocktail bar in the Gramercy neighborhood of Manhattan.

“She walked in the door with a huge smile,” said Mr. Quinn, who had connected with her on the dating app Hinge a couple of days earlier. “She had a warm glow, and a real friendliness to her.”