Yet summaries without that term often sky-rocket: http://news.ycombinator.com/item?id=2002255 And more than one HNer publicly stated that they read comments first, to see if the article is worth their time.

This only make sense if "tl;dr" is considered as a swear word here at HN. Is it?

It's a meme. A meme associated with a different style of commenting. In particular, a "tl;dr" summary is usually a sarcastic over-summary.

I had no idea that "tl;dr" is sarcastic.

My initial comments was meant to be an honest summary.