The panic attacks started after Chloe watched a man die. She spent the past three and a half weeks in training, trying to harden herself against the daily onslaught of disturbing posts: the hate speech, the violent attacks, the graphic pornography. In a few more days, she will become a full-time Facebook content moderator, or what the company she works for, a professional services vendor named Cognizant, opaquely calls a “process executive.”