Originally, "too long, didn't read" was a comment posted on extremely long blog posts that were tedious to read. It was flippantly dismissive without addressing

Originally, "too long, didn't read" was a comment posted on extremely long blog posts that were tedious to read. It was flippantly dismissive without addressing anything the author had to say. It was a way of saying "get to the point". That got shortened to "TL;DR" Then it got adopted by people telling the stories to head off criticism and provide a soundbite version of the story. Basically, here's the whole story if you want, but if you thought it was too long, here's the gist.