[watwut]

And other times, reviewer is doing that to look detail oriented and responsible. He can do that so everybody sees how great and attentive he is. It is opposite of laziness in such case, but still unfair to reviewee.

It is similar with being petty in code review - sometimes people do it because they think it makes them look like better coders.

As for checking business case, yes sometimes you have to do it. But there is also such a thing as doing it too often and second guessing every requirement that you see during code review. This has tricle down effect on analysts/managers/or even customers (he got pissed after a while of this - true story) who then have to litigate and defend every detail and solve programmers conflicts over insignificant details.