College students love social media. But one app especially strikes their fancy. It's called Sidechat and it lets them gossip anonymously about all the latest campus drama. All they have to do is fork over their school email address. Colleges, on the other hand, don’t love Sidechat so much. And members of Congress are increasingly alarmed by its content. A sort of virtual quad where college students across the country sound off on just about everything, Sidechat has played a central role in the House education committee’s ongoing probes into antisemitism at a handful of schools, including the University of...