There are multiple ways of doing something. If the code reviewer leaves a comment for doing something in an alternate way and the person receiving the code resists, then the code reviewer has no right to insist on her/his way. It is then important that to move forward, the team needs to agree on a convention.
Another important part of the code review process is to set conventions. In my humble opinion, the reason conflict happens with regards to code, is due to uncertainty. When there are conventions set up before work on code happens it is to point to code guidelines and say this is what we do. In addition, someone has the ability to challenge code guidelines, and it is more challenging code guidelines. This allows those involved in discussion to save face.
A Time to Learn
It is also very important for others to learn. It is a way for me as the code reviewer to ask what a certain piece of code does. A good convention is that if it is something new that you haven't done before, then you can ask about it and learn about it. This is one of those points that is obvious yet it is passed on more than most.
A Time to Mentor
It is also a time to setup across the app, and specifically make junior developers code owners. Thereby mentoring them and bringing them up to speed on what needs to be done.