it's the whole gimmick of a meme community called 196 where if you visit it, the one rule it has is that you have to post something before you leave

Rule 196 is what I'm assuming you're talking about. It was a subreddit that gained popularity due to only having one rule, which is to post before leaving. The sub started after it's predecessor, r/195, was shut down by the moderators

The history: https://i.redd.it/lgpet1ydu2v71.png

https://lemmy.blahaj.zone/c/196 Rule: You must post before you leave.

It's funny, I never saw 196 on reddit but it really makes an impact in this part of the fediverse!

Thanks for asking OP, I had no idea either.

I know on Tumblr it means 'if you laugh you have to reblog', but judging from the posts on here I didn't think it was the same

To an outsider it's basically just a meme sub, but almost all the post titles contain (or are just simply) the word "Rule".

Lol it's so funny to read the comments about people being annoyed by 195 and 196. It's just old guys complaining that they don't get the joke lol.

It's annoying AF, much like the habit of people posting comments consisting of "Based" all over the place in recent times. The latter is dying down fortunately, and I hope the R meme meets a quick and painful death very soon.