>If reviewer suspects there is a bug, reviewer should check for it instead of having reviewee explain him or defend every detail.
It is not a matter of if the reviewer "suspects there is a bug", but rather a matter of if the reviewer is convinced that there is not a bug.
If the reviewer needs to have someone explain why every minor code change is correct, they are either lazy or incompetent (or the code is badly written). Further, it is generally a bad idea to go to the person who wrote the code to explain why it is correct, as you are then much more likely to make the same mistake the original author made. However, being "okay" often goes beyond correctness, and into business decisions. Often times, these business are not documented (or if they are documented, it is in some management document that is not linked to from the code), so in order to review it, the reviewer has to ask the author what the bussiness consideration that led to the change was.
