Honestly, in my opinion, the fact that this type of thing can even happen suggests the format of code-review has a problem. I propose it's better to:
1. Sit at the desk of the person and pair-code review. Helps avoid basic misunderstadnings, and also is more private that a permanent written record where people may feel defensive about their choices. Also it's easier for a lot of people to be rude through the internet.
2. Write in small notes if any must-address concerns arise and are agreed-upon (e.g. "Security?", "duplicates function x")
If your devs can't interact face-to-face, then I think you've got major cultural problems or hired the wrong devs.