Disclosure: I don’t know the full lore and I’m only answering because nobody else has.

My vague understanding is that this is unique to the ‘196’ community which has a community rule that every post must include the word “rule” in the title post. So it’s super common to see because it’s an active community. Beyond that I don’t really understand what the community is about as it seems to have a random variety of posts.

The 196 community has an (unenforced) rule that you must post every time you visit, so they're posts that are following the rule.