Twitter is having trouble distinguishing between bots trying to meddle in U.S. politics and fervent supporters of President Trump who tweet very often. The micro-blogging company — which has purged fake or suspicious accounts at a rate of 1 million per day for the past three months, including 70 million accounts in May and June alone — has come under fire along with Facebook for sweeping up ordinary and non-robotic accounts in their efforts to prevent Russian disinformation. For instance, 70-year-old Nina Tomasieski spends up to 14 hours per day tweeting the praises of President Trump and his allies while...