Code is logical in nature. It is easy to pinpoint code that is incorrect or could be improved, just like it is easy to notice spelling misteaks. The human condition, when looking at and discussing logical things (like code), is to disregard the feelings of other people. This causes feelings to get hurt and a loss of focus on learning and collaboration.
Improving code review etiquette, because of the human condition, is difficult! Here is a quick list of things that I’ve done, said, seen, or received, that are easy wins in the art of Code Review Etiquette.