NEW YORK — There’s been a lot of talk about the unwritten rules of tennis during Week 1 of this US Open, whether it’s the necessity of a “ sorry, not sorry ” raised hand after a let cord or the proper way to warm up with an opponent or the legitimacy of an underarm serve. Another part of the game drawing attention — thanks to players’ complaints about each of the above — is the post-match greeting at the net, which usually involves shaking hands and, sometimes, a hug or kisses on the cheek. It would seem to be […]... Keep on reading: Unwritten rules of tennis and why handshakes sometimes go awry