We dont have that problem where I work so it does exist. I've sort of experienced something similar myself when I've been doing reviews though - the feeling that you've got to find
something to comment on. I've also been "star-struck" by getting reviewed by someone very senior or "famous" in the open source/tech world and basically blindly doing what they suggest.
The problem we do have though is huge queues for qualified reviewers and getting randomly allocated a reviewer somewhere on the other side of the planet so that even if they have minor comments (e.g. trivial typos in comments) you're looking at a 48 hour turnaround to get your code checked in sometimes.
I guess for the age/hierarchy thing, it could be possible to make the reviews double-blind via the tooling? I.e. reviewers dont know who they are reviewing, and the reviewee doesn't know who is reviewing them. Obviously once the code is committed then everything would become clear and transparent. Might help in larger orgs, although I dont doubt that it would be fairly easy to make an educated guess who is writing the code a lot of the time, and you'd be able to dig into git/whatever to see the details, but just hiding it in the review tool might go a long way to prevent unconscious biases. If someone has a real axe to grind is deliberately going out of their way to find out who wrote the code during a double-blind review so they can make special comments then you probably have a bigger problem.