This might do more harm than good. Often, when reviewing, you will find a problem with the post and want to let the OP know about the problem by writing a comment. You will then look at the existing comments, and it happens often that someone else has already said what you wanted to say. For example,
what have you tried?
is this a homework question?
A secondary points or ranking system.
This already exists, in the form of badges (Custodian, Reviewer and Steward). There's a badge progress bar at the top of the page; you can click on it to show more badges you can earn:
These count towards your candidate score if you would want to run for moderator at any point in the future.
Also, there is a form of ...