Popular Science's explanation of why they shut off comments is worth reading: http://www.popsci.com/science/article/2013-09/why-were-shutting-our-commentsA politically motivated, decades-long war on expertise has eroded the popular consensus on a wide variety of scientifically validated topics. Everything, from evolution to the origins of climate change, is mistakenly up for grabs again. Scientific certainty is just another thing for two people to "debate" on television. And because comments sections tend to be a grotesque reflection of the media culture surrounding them, the cynical work of undermining bedrock scientific doctrine is now being done beneath our own stories, within a website devoted to championing science.
I was pleased to read that. It's interesting that what long was considered to be quality control is now considered to be censorship. I find nothing wrong with a scientific publication hosting only those discussions that demonstrate a grasp of the matter at hand. That's not censorship, it's keeping ignorant blather from detracting from a conversation with ends that don't include explaining the fundamentals to people that aren't interested in them.