>>How can my feedback improve you as a software developer if you don't understand your own code?

> Just say that you don't want my code, better yet just silently reject it.

These decision points are orthogonal, in that the author identifies a social contract wherein a contributor must have an understanding of the change-set they submit in order for it to be a viable candidate. Determining if the submitted change-set is applicable/appropriate/correct and how to provide feedback to the contributor is a subsequent activity.