I think that Slashdot's comment system sometimes works extremely well. The speed with which it splinters off into snarky tangents sometimes makes it worthless.
Natalie Portman and oatmeal are dead, Netcraft confirms it. Slashdot fails as a news site because it's slower than everyone else, the best comments are redundant because everyone reading slashdot is also reading reddit and hackernews and LtU and ..., and because Slashdot is the last to post the interesting comments have already been made. Even its memes are stale. CmdrTaco himself gave up on it after the OMG Ponies! april fools thing. The moderation system is clever, but the community just kind of froze somewhere between 1999 and 2006. It's sort of comforting, because geek culture has gotten a lot less fun in the mean time if it's still even a thing outside of marketing, and Slashdot is a sort of unliving Pompeii that's a lot like the good old days except with more dust and ambulatory corpses, but it's not "stuff that matters" anymore.
And really, all of this is compounded with the current ownership structure at Slashdot. Dice has been destroying a lot of good faith with their moves at SourceForge, and ThinkGeek's sale to Gamestop. Slashdot is pretty much living on borrowed time.
About a year ago, the issues at Slashdot came to a head with the botched rollout of the new "beta" interface. The redesign reflected a complete disconnect from the community, and prompted a large scale "slashcott" boycott/revolt. This ended up resulting in the creation of SoylentNews, and the migration of a chunk of the community. Dice has continued to demonstrate a complete lack of understanding and simply rolls forward with more additions of sponsored content, video content that no one asked for, and most recently, outright replacing the "Read the [n] comments" link with a social media "share" button. I see a LOT of parallels with the situation at Reddit.