This is the issue. It's not that this is "LLM writing style". It is just formal writing. The thing is most people write like third graders, so these stick out with good reason, just not that 'it is AI'.

In general there aren't good ways to tell TBH. Literally giving it the command to 'not write like an AI' would make half of these disappear.

Having the AI edit a text for you would add some of these. Not because it is AI, but because that's proper writing.

I don't think it's necessarily just a checklist of things, but rather the way an LLM's output resembles these techniques that puts it into an uncanny valley of writing. As a writer, you use these techniques deliberately and thoughtfully. LLMs can't do that, so the output just feels off.

where do you think they learned it?

Maybe you're actually a llm? And you're slowly learning to disguise that you are by using --

Same. I used to write articles for an industry mag and that's how I was taught to do it.

Some word processing apps automatically convert two dashes to an em dash. I've got that turned off right now.

"em dash" isn't hyphenated, fyi.

You can take em—dash out of my cold dead hands