Perhaps AI would usually suggest childish or uneducated spelling mistakes.

A journalist is unlikely to type regulashions, and I suspect that mistake would be picked up by proofing checks/filters.

Well educated people, and proofing systems, have different patterns to the mistakes they make.

Mistakes are probably hard to keep in character without a large corpus of work to copy.

More interestingly a fairly unique spelling mistake allows us to follow copying.

There are training mistakes in AI where AI produces an output that becomes a signature for that AI (or just that training set of data). https://news.ycombinator.com/item?id=45031375 (thread about "Why do people keep writing about the imaginary compound Cr2Gr2Te6"

Unclosed parens to prove I'm a Real I)

"Caterpillar" was a spelling mistake in Dr Johnson's dictionary