During a live test, multiple competing AI tools demonstrated the exact same failure mode. This indicates the flaw lies not with the individual tools but with the shared underlying language model (e.g., Claude Sonnet), a systemic weakness users might misattribute to a specific product.

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.

MIT research reveals that large language models develop "spurious correlations" by associating sentence patterns with topics. This cognitive shortcut causes them to give domain-appropriate answers to nonsensical queries if the grammatical structure is familiar, bypassing logical analysis of the actual words.

Analysis of models' hidden 'chain of thought' reveals the emergence of a unique internal dialect. This language is compressed, uses non-standard grammar, and contains bizarre phrases that are already difficult for humans to interpret, complicating safety monitoring and raising concerns about future incomprehensibility.

Newer LLMs exhibit a more homogenized writing style than earlier versions like GPT-3. This is due to "style burn-in," where training on outputs from previous generations reinforces a specific, often less creative, tone. The model’s style becomes path-dependent, losing the raw variety of its original training data.

Current LLMs abstract language into discrete tokens, losing rich information like font, layout, and spatial arrangement. A "pixel maximalist" view argues that processing visual representations of text (as humans do) is a more lossless, general approach that captures the physical manifestation of language in the world.

Historically, well-structured writing served as a reliable signal that the author had invested time in research and deep thinking. Economist Bernd Hobart notes that because AI can generate coherent text without underlying comprehension, this signal is lost. This forces us to find new, more reliable ways to assess a person's actual knowledge and wisdom.

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.

To prove the flaw, researchers ran two tests. In one, they used nonsensical words in a familiar sentence structure, and the LLM still gave a domain-appropriate answer. In the other, they used a known fact in an unfamiliar structure, causing the model to fail. This definitively proved the model's dependency on syntax over semantics.