The humor is why I also browse Slashdot, even though they're generally late (like by days) with the submissions. There's a little bit of serious discussion, a lot of memes, but then some generally humorous discussions based off misinterpretations of comments, articles, and titles.
* First comment debunks the article.
* Comments that start with "No." It's worse if the "No." is in its own paragraph.
* Mentioning Maslow's hierarchy of needs.
* General passive-agressivness.
* Lack of humour and light-heartedness.
* People upvote some really shitty stuff. The newest submissions page is sometimes more interesting than the homepage.
* People love to upvote blogposts of some people, e.g daringfireball.net or paulgraham.com, no matter the quality.