The boos continued, and so did Daniil Medvedev’s U.S. Open run. The fifth-ranked Russian, the villain of the tournament, will take that trade-off. He reached his first-ever Grand Slam quarterfinal Sunday night and didn’t mind how he has been received by the Flushing fans. After the winning point, he danced, further angering the crowd. As he did Friday night, Medvedev egged the fans on in his on-court interview, thanking them for motivating him with their jeers. “After the match, I engaged a little bit with the crowd,” Medvedev said after topping Dominik Koepfer, 3-6, 6-3, 6-2, 7-6 (2), at Louis Armstrong Stadium, advancing to face No. 23 Stan Wawrinka. “But we all know how [the] New York crowd can be. It’s probably the most electric crowd in the world, I think. Especially, I mean, playing this week on big courts, I could feel it. Today I was just engaging with the crowd and hopefully — hopefully it was fun for them and for me. As I said, it gave me a lot of energy to win.” His vill...