Originally Posted by FlyingMonkey
This is entirely untrue. As with any other accessory, it may be appropriate or not given the wider context, and the specifics of what else you are wearing. In some circumstances a square can give a perfect lift to an outfit, in others it can be the straw that breaks the camel's back... and that's really all you can say.
My assertion is neither "true" nor "untrue", since it's neither provable nor unprovable. It is, however, an opinion that is well supported by the commonly cited authorities on the subject of classic menswear. I'm thinking here of Will and Manton, and also of Flusser, who seems to take an even more orthodox stance than I do:
Without some form of pocket rigging, an outside breast pocket appears superfluous, and the outfit incomplete.
(Dressing the Man, page 213.)
While there are situations where the addition of a pocket square might make the outfit look overwrought, my opinion is that if the outfit cannot even accommodate a plain white hanky, the problem probably lies with the rest of the outfit, not the hanky.