Here on HN, you occasionally find tl;dr near the top of a comment thread -- but it's followed by a nice summary of the article. Instead of expressing the rather worthless sentiment of "I didn't read this", it's expressing the far more valuable "if you're not sure you want to invest the time in reading this, here are the highlights of what you would have otherwise missed."

Speak for yourself.

I'll often read the comments briefly first before deciding if I want to read an article.

While tldr summary is certainly valuable, asking for one without even bothering to form a single sentence is the same level of spam as +1 type of .

I totally agree, I don't read the comments for an explicit summary. I read the comments to see what opinions people have of the article, on the basis of the comments I determine if the article is worth reading.

I don't do this for all articles, but it is a pretty common occurrence.