Why AI Loves the Em Dash: The Markdown Theory

For a year, writers have joked that the em dash is AI's fingerprint, but nobody could say why. A newly cited 2026 research paper offers an answer: the habit may be markdown formatting leaking into plain prose, picked up because high-quality training text is disproportionately markdown-formatted, where dashes double as visual separators. See the paper's replication data at SlopDetector and check your own drafts with our draft checker.

Meanwhile Wikipedia's editing guide now has a formal name for another familiar tic: negative parallelism, the "it's not just X, it's Y" move our trend board has tracked since launch. EQ-Bench's public Slop Score page confirms the pattern still carries real weight in AI-detection math, worth twenty-five percent of its composite score alongside overused words and stock three-word phrases, as described at EQ-Bench.

None of this proves any single sentence is AI-written; human writers use dashes and contrast sentences too, just less often and less predictably. What is useful is noticing the pattern in your own drafts before you hit publish. Run a paragraph through our fix-your-ai guide and watch for dashes doing work a comma used to do, or a sentence that sets up a strawman just to knock it down.