Other people might point to more specific tells, but instead I'll reference https://zanlib.dev/blog/reliable-signals-of-honest-intent/, which says that you can tell mainly because of the subconscious uncanny valley effect, and then you start noticing the tells afterwards.

Here, there's a handful of specific phrases or patterns, but mostly it's just that the writing feels very AI-written (or at least AI-edited). It's all just slightly too perfect, like someone's trying to write the perfect LinkedIn post but are slightly too good at it? It's purely gut feeling, but I don't think that means that it's wrong (although equally it doesn't mean that it's proven beyond reasonable doubt either, so I'm not going to start any witch hunts about it).

But here's the thing. The LLM house writing style isn't just annoying, it's become unreadable through repeated exposure. This really gets to the heart of why human minds are starting to slide off it.

Not trying to be rude but your very short reply is hard to understand. "Unreadable", "starting to slide off", I honestly don't know what you're saying here.

Pretty sure they are mocking LLM outputs by making their own comment look like as if it came from LLM. It's sarcasm.