Finessing Typographic Details: Positioning Punctuation
http://www.itcfonts.com/Ulc/4012/PositioningPunctuation.htm

Strizver, Ilene
Upper and lowercase Magazine
2007

Abstract:

Are your characters depressed? When punctuation marks are positioned next to ALL CAPS, it can leave them looking a little low. Even making small adjustments in a character’s position will create greater visual balance and give your layout a “lift,” especially in display sizes.