Before jumping in with your thoughts on how managers should or should not be involved in code review, note that this is about code review review. Reviewing the code review process, and reviewing the code reviews.
I think you've said the most key thing here. Much of the HN conversation has drifted out of focus.
The best management I've seen was tapped into the pulse of the team and knew how people interacted and the problems we were struggling with. Keeping an ear to code reviews is no different than observing how your team interacts in person or in emails.
