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“I Am the Gap Between Knowing and Saying”: The En Dash Responds to the Em Dash
“I Am the Gap Between Knowing and Saying”: The En Dash Responds to the Em Dash

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“I Am the Gap Between Knowing and Saying”: The En Dash Responds to the Em Dash

Commented Bringhurst thus:
(The Elements of Typographic Style, 2004, § 5.2.1)
But [space][endash][space] is longer than just [emdash]. How is the proposed solution any better?
It depends on the font whether an em dash is longer or shorter than an en dash surrounded by spaces. But Bringhurst's comment is more about aesthetics. I also find the en dash with spaces visually more pleasing and more logical to set parenthetical sentences apart, rather than the em dash without spaces. The latter invites me to join sentences.
But it's all a matter of personal tastes of course! :)