A deep unease trickled through Jacob Glick’s entire body. He had started a virtual deposition of Jim Watkins, the large, scruffy QAnon conspiracy theorist who runs 8kun, a website filled with hateful, racist content that included calls for violence at the Capitol on Jan. 6, 2021. Glick, then an investigative counsel for the House select committee probing the Jan. 6 attack, made the customary introductions of his colleagues. Watkins jotted down all the names. “It already felt creepier — and I’ve been in some creepy ones,” Glick said. Glick was among the staff on the now-disbanded Jan. 6 panel who...