No suit needed: soft corners I can live with, easily; blurry edges I simply hate!
In some ways I quite agree. Soft corners, whether they are due to the optical design and performance of a lens or possibly interaction with the extreme pixels and their design on a given density packed high resolution sensor are generally and specifically easier to deal with than bluffy, smeared corners.
With soft corners, if their sharpness does become important to a particular image, they can often be isolated and additionally sharpened to a degree and matched (blended in) to look natural to the adjacent part of the image. Conversely, smeared blurry corners look exactly like "smeared blurry corners" and no amount of post processing is going to return that part of the image to look in it's natural state....whether it be a brick facade or a well defined structure or recognizable element.
As a general rule, blurry smeared corners often indicate optical misalignment, where soft corners are often attributed to resolution falloff of the lens in general...although with so many different sensor designs (specifically their pixels with regards to pixel density and micro-lens design), these blurry corners may have their origins (or part thereof) due to lens/sensor interaction.
With that said Jack is "right" for the most part....for these blurry corners to be seen or have a degrading impact on the image (beside pixel peeping at greater than 50%), a substantial enlargement/print has to be made or at the very least the image initially cropped significantly to reveal the details of one of those corners.
EDIT #1 : As for the importance of these blurry corners I am reminded of the example of an extraordinarily beautiful "classic car" that has less than perfect front fenders. If the fender's paint is simply duller than the rest of the car, some high gloss, somewhat abrasive car polish might help it blend in with the rest of the car. It may be a little destructive but it will look better and more natural to almost everyone, even discerning connoisseurs, as opposed to doing nothing. If the car instead had small dents in the fender, no amount of polish will help. How important are these dents? To the owner, and "fender peepers"...very!
To the general public or those who admire the entire car for it's outstanding beauty and look at it as a whole, the fenders themselves are hardly noticed, if that....LOL!
EDIT #2: I can just see it now. Jack and Tim are involved in a small fender-bender car accident. Tim says "Jack look, just look what you did to my beautiful car's fenders, their dented! See how distorted they are? I can't stand the way they look!". Jack replies "Tim, take it easy, it's only the fenders...and besides, fenders are highly overrated anyway" :ROTFL:
Dave (D&A)