After 123 years of recommending restaurants to road trippers, the Michelin Guide is driving into the hotel world. At an event on Thursday, October 5 in Paris, the eponymous publication owned by the French tiremaker announced that it would start designating “the most exceptional hotels across the world”—not with one, two or three stars but with a “key” emblem. It will allocate keys to establishments based on five criteria: having a local character, individuality, excellence in architecture and interior design, top service and comfort,...