Before boarding my flight to Boston late last month, I spent the better part of three days doing something I never imagined I would do in more than 30 years of covering China: scrubbing my phone. Old emails, screenshots, WeChat threads that might be read the wrong way, anything that could be misconstrued in an airport interview room – all deleted, just in case.I was not being paranoid. I was following advice now routinely passed among Chinese travellers to the United States: carry a clean...