Ever go through somebody's code, see some weird construct, go "this person is an idiot!," rewrite it, and find some edge case bug that the original code was written to handle? The original author had many of the same ambitions as you, and you relearned all the same lessons she did -- the hard way.
Recognizing and curtailing this impulse leads you toward enlightenment.
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.
Recognizing and curtailing this impulse leads you toward enlightenment.