Moonlighting under the name Roaring Kitty, Keith Gill became something of an online folk hero for his dedication to GameStop, the struggling video-game retailer at the center of a trading frenzy that sent its share price into the stratosphere.But now a regulator in Massachusetts wants to know more about Mr. Gill, a registered securities broker, and his former day job as a financial wellness education director at an insurance company based in Boston.Inspired in part by Mr. Gill’s cheerleading, thousands of small investors pushed stock in GameStop to as high as $483 a share and made Mr. Gill …
