If the original programmer fixed some edge case and didn't bother to flag this in the code by means of comments then they worse than an idiot, they are incompetent. As would be the second programmer if they neglected any such comments which were there.
>If the original programmer fixed some edge case and didn't bother to flag this in the code by means of comments then they worse than an idiot, they are incompetent
If every reason for every fix based on an unanticipated logic path was commented, there would be 10x more comments than code.