Hey Reader, Six years is a long time to disappear from the stage. In Céline Dion’s case, “disappear” involved being diagnosed with stiff-person syndrome, a rare neurological disorder that causes severe muscle stiffness and spasms. It affected her ability to walk, move, and use the voice that had made her one of the world’s biggest singers. For years, nobody knew whether she would ever perform a full concert again. Then, last Saturday, she walked onto a stage outside Paris in front of roughly...