Corner flaws impact the grade as opposed to merely being qualifiers like centering.
If one wants to go crazy, there are about 100 ways to analyze corners. Bottom line,
if you find yourself squinting or using various scoping devices to analyze a corner,
you are probably dealing with a card that has nearmint or better corners. Scoping
devices are needed to separate nearmint from mint which I am not going to spend time
Touched/Soft Corners: Just as it sounds, the corners are visibly not perfectly square but clearly not an eye sore either.
Rounded Corners: Much more worn than toucher or soft. Actually appear rounded and hardly lack the look of a right angle bend.
Blunted Corners: Caused most likely by the card being dropped or pressed against something causing in effect, a crease but near the corner of the card. In general, distinguishing a crease vs a blunt isn't a worthy distinction since both drop the grade in the same manner.
In general, 2 or more touched/soft corners start to drop an overall grade of a card below nearmint. Any blunted or rounded corners drop a card below Ex+. See the overall grading matrix for more information.
Examples of Corners: