You also have to take into account that the medium is the message[1]. In a nutshell, the more people read LLM generated posts and interact with chatbots, the higher the influence of LLM style in their writing -- the whole "delve" comes to mind, and double dashes. So even if you have a machine that correctly identified LLM generated posts, you can't be sure it'll keep working.
[1] https://web.mit.edu/allanmc/www/mcluhan.mediummessage.pdf
Let's say you are the LLM detecting genius you paint yourself to be. Well guess what? You're human and you're going to make mistakes, if you haven't made a bunch of them already. So if you have nothing better to add to a post than to guess this, you probably shouldn't say anything at all. Like you said, it's not even against the rules.