Step aside, Passive Aggressive Notes. Subtweets: You’re way out of your league. From Britain, the ancestral home of dry humor and repressed feelings, comes the pinnacle of Internet passive aggression — and it must be seen to be believed.

The site in question is called OpnLttr.com, and it allows anyone to write a letter to anyone else — and post said letter publicly. Since 2012, when Londoners Russell Hart and Peter Ruppert launched the site, its served as clearinghouse for thousands of simmering, and often anonymous, grievances. Sometimes those grievances are quite serious: OpnLttr’s most-read post to date is a message from an abused woman to her ex-husband’s new girlfriend. Sometimes they’re trivial, as in Richard Orbin’s popular open letter to a “Nigerian prince.”

But the best ones, if you dig for them, are drama of the very highest order: letters to cheating boyfriends, backstabbing friends, childhood bullies, workplace crushes. It’s an equal mix of heartbreak and hilarity — the text equivalent of reality TV.

“It appears to attract people who share their deepest emotions and deepest secrets,” said Ruppert, one of the founders of the site. “Stories that never before had a platform that allowed them to see daylight.”

Social media, of course, has a special talent for dragging out these kinds of stories, particularly since anonymous-sharing apps like Whisper and Secret became trendy last year. Everyone’s unloading secrets on Tumblr, or sub-Facebooking their ex in song lyrics, or making public pronouncements on the behavior of other people/companies/groups. Confession sites and rant forums proliferate: Simple Confess, Raw Confessions, E-admit, Rant Rampage.

“Online, people can be rewarded for their expressions of anger,” the PBS NewsHour once concluded. It seems like a uniquely modern development, in other words.

But I like OpnLttr because it’s a fun reminder, in its unabashed literalness, that the opposite is actually true — that people have, in fact, subtweeted since the Romans, in a certain nonliteral manner of speaking. The open letter is an old art form. While the term itself dates to 1798, people wrote open letters long before that — Paul to the Corinthians, Martin Luther to all of Europe. (Much later, his namesake — Martin Luther King Jr. — would write a history-altering open letter “from Birmingham Jail.”)

But even if we used to address open letters more to politicians or religious congregations or something similarly highbrow, that doesn’t change their essential confessional and/or confrontational purpose from what they’ve become now.

OpnLttr is still a relatively small site: It only sees about eight new letters a day. Many are by the same posters, Ruppert said; people who find the experience so cathartic or validating that they keep writing new letters, again and again. Ruppert doesn’t discourage this kind of repeat posting — on the contrary, he says, he started OpnLttr to give the same kind of public platform to personal grievances that was previously reserved for public figures and politicians.

TMI? Maaaaybe. Redundant? Sure. But personally, I see the appeal. Editorials are well and fine, but it’s far more fun to read “open letters” from ordinary lives.

Caitlin Dewey runs The Intersect blog, writing about digital and Internet culture for The Washington Post.