The piercing pop-pop of pickleball paddles starts before sunrise and ends after midnight at dozens of newly built courts across Hanoi, as residents relish one of Vietnam’s fastest-growing sports – or rage at the noise it makes. The initial craze saw more people in Vietnam pick up a paddle per capita than anywhere else in Asia, according to one survey. Now unwitting spectators are yelling fault, filing noise complaints and petitions to curb playing hours that have left authorities in a pickle. In...