# LLMs could write like humans but post-training guardrails make their text detectable

> Source: <https://the-decoder.com/llms-could-write-like-humans-but-post-training-guardrails-make-their-text-detectable/>
> Published: 2026-08-20 17:36:51+00:00

# LLMs could write like humans but post-training guardrails make their text detectable

**LLMs could theoretically write as diversely as humans, but they don't.** Post-training and safety guardrails keep their text detectable, argues Bradley Emi, CTO of AI text detector Pangram, in a [blog post](https://pangram.substack.com/p/no-llms-dont-just-mimic-human-text). Systems like ChatGPT, Claude, or Gemini learn behavioral rules to avoid dangerous outputs or censor certain political statements. This sharply narrows their expressive range, an effect called "mode collapse."

So-called base models, the raw models before post-training, write with more variety, so Pangram's detection doesn't flag them, Emi says. The [same goes](https://x.com/max_spero_/status/2089938824474263644) for narrowly specialized fine-tunes trained only on Hemingway or certain subreddit texts, and for broken outputs like incoherent text. This only applies to non-watermarked AI text, though. [Watermarks will likely always work](https://the-decoder.com/anthropic-watermarks-claudes-output-but-critics-question-the-tradeoffs/), even with a base model's variety.

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[Pangram](https://pangram.substack.com/p/no-llms-dont-just-mimic-human-text)