I don't recall many, if any, Github repos containing this emoji-vomit before the rise of AI, and likewise natural human conversations in forums and such were also not like this, so I find it very odd and distinctly unnatural. Where did this "vibe coded" style actually originate from?

I occasionally saw a readme with a couple of Emoji in it, but the behavior where every title, every bullet point, every sentence ends with one or more of them is utterly obnoxious. There's something about the sources that chatGPT uses which causes it just sprinkle Emoji absolutely everywhere, it's one of the most obvious tell tales that it came from chatGPT without a prompt to tell it otherwise.