The tell tell sign for me is that it's still incredibly hard to read. AI tend to write in a style that I'm unable to easily read (humans does that as well sometimes). I constantly have to go back and re-read the previous sentence, because the text simply doesn't register.
A next step I'd suggest is asking the LLM to use shorter words when available.
Did you check this? https://huggingface.co/sam-paech/gemma-3-27b-it-antislop
LLMs as a word generator love generating words, and that includes generating bigger words when simpler ones will do.
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I found the coffee shop one telling. Both suffer from being a stream of bland statements. The original version is actually reasonable if you just excise the Claude-isms. The rewrite has a whiff of ASD-STE100, and reads like the sort of sentences one would write for homework while learning a new language. There is also almost no difference between the de-slopped opinion piece and the blog post.