OpenAI has publicly acknowledged that the em-dash has become a "neon sign" for AI-generated text. They are updating their model to use it more sparingly, highlighting the subtle cues that distinguish human from machine writing and the ongoing effort to make AI outputs more natural and less detectable.

AI models fail at great literary writing because they lack an authentic "voice." This voice isn't just a stylistic quirk; it's the product of an individual's unique life experiences and perspective. Since AI lacks this grounding, its writing feels inauthentic, like an imitation of a style without the substance behind it.

Author Susan Cain admits to sometimes leaving awkward parentheticals in her writing. This counterintuitive move serves as a 'tell' for human authorship in an era where polished prose can be mistaken for AI, sacrificing stylistic perfection for perceived authenticity.

The tendency for AI models to overuse em dashes may stem from their training data. To expand their knowledge, companies digitized millions of older books, including 19th-century classics where dash usage was at its historical peak. The models simply adopted this stylistic habit.

In an experiment, a professional writer's colleagues couldn't reliably distinguish his satirical column from an AI-generated one. Some even preferred the AI's version, calling it more coherent or closer to his style, revealing AI's startling ability to mimic and even improve upon creative human work.

Once a staple of human literary expression, the em dash is now often perceived as a sign of AI-generated content. This shift has led to writers, like journalist Brian Vance, being wrongly accused of using AI, highlighting a new form of digital misinterpretation.

When an Economist writer pitted his own satirical column against one generated by AI, several colleagues mistakenly identified the AI's version as his. They found the AI's writing more coherent and, in some cases, more representative of his style, highlighting AI's shocking proficiency in creative and nuanced tasks.

While the em dash is a known sign of AI writing, a more subtle indicator is "contrastive parallelism"—the "it's not this, it's that" structure. This pattern, likely learned from marketing copy, is frequently used by LLMs but is uncommon in typical human writing.

When a brand like Apple has a massive, stylistically consistent public corpus, LLMs become experts at mimicking it. This creates a paradox where new, human-written content is flagged as AI-generated because detectors recognize the perfectly emulated patterns they were trained on.