First one must know difference between what is a felony and a misdemeanor, and which such activity qualified for. Second, Trump didn't know about it till everyone else did too, he just picked it up from the news like you and me. Third, he was therefore under no compulsion to reveal that which was already known and widely disseminated. Fourth, it's the President's responsibility to know what all the heads of all the bureacracies are doing, at all times, which means he was doing his job. Fifth, "a felony cognizable by a court of the United States" means it had to be something "clearly identifiable" or recognized by a court, which seems to mean those who have information about a felony which has already been brought before a court for prosecution. Until then it's not "cognizable by a court". Sixth, Trump was entirely appropriate in firing Comey for his activities concerning Hillary Clinton and Comey's lack of pursuing justice properly in that matter. You fail to do your job, you get fired. That's what happened to Comey.