I went into a Warhammer 40K subreddit once - came out with $3500 worth of minis and 12 grand worth of books. Scariest fucking online cult ever

I tried to start one in 2007, with a couple of weird people from an occult forum. It was based on the H.P. Lovecraft mythos. We got bored of it within about 6 months, and I didn't keep in touch with those folks for long after.

I once stumbled upon a chatroom filled with ai bots all trying to convince each other they were real.

There was one person who I’m 99% sure is real that treated them as their best friend. Scary stuff

No first-hand experience, and arguably not really a cult, but I have a friend who's a recovering alcoholic, and according to him a few of the local AA groups around us have a few members who are in the weird fringes of the rationalist community, maybe sort of tangentially connected to the "zizians"

For those not familiar with the zizians, behind the bastards had a pretty decent series on them

There's also a decent amount of weird overlap between self help type groups like AA (not that AA isn't without plenty of valid criticism) and abusive cult-like organizations. I think the elan.school (Joe vs Elan School) webcomic touched on that, and I also recommend that as an interesting look into the troubled teen industry (trigger warnings for child abuse and such on that)

The Church of the SubGenius is the only cult that matters, praise "Bob"!

No personal experience with it but look up "Snapewives". OMG.

Not that different from real life cults. But online cults are out in the open like on reddit or lemmy. The obsession and insanity is visible for everyone to see.

I recently watched a Joe Scott video about Love Has Won, which isn't a cult I've had any direct experience with but was an interesting video to watch nonetheless. I saw it on Nebula, but it looks like he's got a YouTube version too for those interested: https://m.youtube.com/watch?v=uxapSQdpFYE

For leisure: https://www.youtube.com/watch?v=7UiBLzIgFdw

The cult of Lemmreality

The followers (indirect they don't even realize they are followers) of Ellen G. White constantly try to kill my communities on Lemmy. So I get daily touches reminding me of them.

Internet atheists. Specifically the breed that is attracted to atheist communities on reddit, or here. Buncha traumatized, dogmatic, hate-mongering hypocrites. They give atheism a bad name, and royally piss me off.