…ut it occurs to me that one big power of today’s standalone subordinate clause is that it’s punchy. Because it alludes to utterances that stand outside the clause — and the reader fills in the blanks — it compresses a lot into very few words. That works nicely in smartphone environments where space is tight, and brevity is the soul of wit.
A historic parallel? The crazy, long chapter headings in 19th-century novels, which often were also dependent clauses, inviting the reader to imagine the rest of the baroque narrative. “In Which Our Protagonist Meets A Dashing Stranger,” McCulloch jokes. “The ‘in which’ is doing a very similar thing.”