A parenthetical sentence is a paradoxical thing. It straddles worlds: It is both inside and outside the text simultaneously, included and excluded. It is not quite important enough to merit the full center-stage spotlight but also not unimportant enough to be shoved entirely behind a curtain. A pair of parentheses is the sound of a text leaning over and whispering to us.
Sam Anderson, “New Sentences”, The New York Times Magazine (20 August 2017), 11.