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99% Invisible
99% Invisible

The Em Dash

February 03, 2026 • 39m

Summary

⏱️ 9 min read

Overview

99% Invisible explores the fascinating history and cultural significance of the em dash, from its theatrical origins with Shakespeare to its controversial association with AI-generated text. The episode traces how this versatile punctuation mark became a defining feature of great literary works by Emily Dickinson, Jane Austen, and others, before becoming stigmatized as a potential indicator of AI writing. The story includes a contemporary solution: the Am dash, a specially designed punctuation mark that humans can use to prove their writing is authentic.

The Reddit Accusation and Em Dash Controversy

Portland journalist Brian Vance, who runs Stumptown Savings newsletter about local grocery deals, found himself accused of using ChatGPT to write his content simply because he used em dashes in his writing. The accusation highlighted a growing cultural phenomenon where the em dash has become associated with AI-generated text, despite its centuries-long history in human writing. This modern stigma around the em dash sparked a larger conversation about how we identify authentic human writing in the age of AI.

  • Brian Vance spends 40 hours a week writing his Stumptown Savings newsletter helping people fight corporate greed and inflation
  • A Reddit user accused Brian of using ChatGPT, citing his use of 'extra long em dashes that are not possible to replicate on a normal keyboard' as evidence
  • The em dash is a versatile punctuation mark about the width of a capital M that can replace commas, colons, semicolons and parentheses
  • Large language models like ChatGPT, Claude, and Gemini have been sprinkling em dashes in their responses 'like digital confetti'
" I spend 40 hours a week doing this. Just trying to help people, like, have some say, have some power in what feels like a powerless struggle with, you know, corporate greed and inflation. "
" There are some people who look at it and be like, well, an AI must have did this because why would a human use an M-dash? But, you know, I'm a human. I can confirm. "

Medieval Origins: Boncompagno's Punctuation Innovation

The em dash's origins trace back to 12th century Italy and a scholar named Boncompagno da Signa, who practiced the formal art of composing letters. Frustrated with inconsistent punctuation systems of his time, he created his own simplified system including the virgula plana, a horizontal dash that looked exactly like a modern em dash. While his comma-like mark succeeded, his dash as a sentence ending didn't catch on, but it set the stage for the mark's future evolution.

  • Before the 12th century, there wasn't a good set of rules for punctuating texts that persisted or was usable across different contexts
  • Boncompagno da Signa created the virgula plana, a horizontal dash that looked exactly like a modern em dash, originally used to end sentences
  • His comma-like forward slash mark succeeded and evolved into the modern comma, with 'virgola' meaning comma in Italian
  • The dash remained grammatically unclear and malleable for centuries, giving it freedom for experimentation

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