I'll go first: r/kitty. One of the hundred grillion cat subs back on Reddit, the culture in this one was you posted a cat picture, and the only word allowed in the title or in any comments or replies was "Kitty."
Someone is using that subreddit for covert communications, I just know it. Either on the level of "if u/PM_me_your_nostrils posts an orange cat, we attack at dawn!" or there's some steganography going on with the pictures, but that subreddit was too stupid to be as active as it was.
Also related to reddit, since that's where I was always inundated with this shit, before moving here: the constant stream of Genshin Impact leaks that come out, that the whole obnoxious subculture is built around, are just released by Mihoyo, intentionally, under the guise of all the anonymous leakers that constantly come and go. Seems to me like the only explanation for how CONSTANTLY leaks come out, and how they're basically never actually damaging to the game or the company, while being REALLY effective at stirring up obsession in the fanbase, and driving people to invest more time and money into the game to be prepped to get the next new character immediately on release.
Also how so many of the leakers would release extremely accurate stats and numbers, but then drop statements like "if I release any more than this, I'd be risking my safety" or "since everyone's been asking about it, I'll go ahead and confirm X, but after this I'm gonna have to go on hiatus for a while, until things cool down". Seems like nonsense meant to either inflate the leaker's ego, or rile up the fanbase.