Corsi is NOT a measure of defensive prowess. It is a measure of shots for/against. This is why Gogo was and still is a Corsi monster on D. It is better to play "defense" in the other team's zone. It also doesn't take into account any shot quality for/against. This is why Crosby's corsi is better than TK's corsi. This is also why the Pens had to part ways with Michalek for basically nothing. He was/is a poor defensively player.
The corsi rel qualcomp list is only the "adjustment" that is added/subtracted to the raw corsi numbers. It is not very significant. Zone starts adjustments (which unfortunately aren't accounted for anywhere on behindthenet) are absolutely critical. Nothing impacts your corsi numbers more than where you start your shifts.
The bolded doesn't make any sense to me. Because it doesn't take into account quality of shots, Crosby (the guy with a good shot) has a better corsi than Kennedy (the guy who shoots from everywhere).