The core problem is that code reviewing is leadership, supervisory/gatekeeper function as any other, kind of like editor and should be treated as such. Even if reviewer and coder are formally at same footing or switch functions, it is momentary it. So, treat it as such and expect people to treat it as such. Meanwhile, people in tech talk about it in idealistic terms that are sometimes true, but often not.
1.) Don't use code review to teach juniors, talk with juniors in advance and supervise them as they go. If they learn about major architectural problem in code review, you are senioring wrong.
2.) Don't try to tech colleges in code review or use code review to force new standards on ad-hoc basis. Talk about issues in standards before, teach colleges as you go around your day without holding pull requests (and their weekends in work) hostage. If your only communication about these issues is code review, you are doing it wrong.
3.) Don't assume that code reviewer is automatically right just by its function and don't let code reviewer to steal responsibility from coder. Don't assume opposite either (through assuming opposite is better). Don't make discussion a taboo.
4.) Difference in opinion is normal and does not mean one of the people in conflict is idiot.
5.) Passive aggression does not belong to code review. Don't lie in code review comments either. "This is objectively horribly wrong" counts as lie if you are using it to push for personal preference and not ready to defend it. If you say or imply in your code review comment that someone is lesser coder, it is ok for that person to challenge the assumption and defend himself.
6.) Keep your own emotions out if as much as possible. If the code is making you angry, is it objectively bad or just something you are personally unused to (new syntax can be annoying even if it is good)? Distinguish the two.
Code review should be about one things only: Is this good enough to go to codebase? Is this required change a blocker or minor thing (variable naming)? All the other functions can be a bit helped by review, but absolutely should not be seen as review purpose.