In many countries, cursing online about the government is so commonplace nobody bats an eye. But it’s not such an easy task on China’s heavily censored internet. That doesn’t appear to have stopped residents of Guangzhou from venting their frustration after their city — a global manufacturing powerhouse home to 19 million people — became the epicenter of a nationwide Covid outbreak, prompting lockdown measures yet again. “We had to lock down in April, and then again in November,” one resident posted on Weibo, China’s restricted version of Twitter, on Monday — before peppering the post with profanities that included...