Among those most intently following the House Jan. 6 committee hearings is Stewart Rhodes, the jailed leader of the Oath Keepers militia group, which was on the scene at the Capitol riot. The former Army paratrooper and Yale Law School graduate turned militia leader now spends 22 hours a day in solitary confinement and has had little contact with the outside world since he was jailed in January on charges of seditious conspiracy. He has not been deprived, however, of the panel’s highly publicized hearings, which echo in his otherwise spartan cell. “I’ve watched or listened to all of them,”...