It wasn't a decision we made lightly. As the news arm of a 141-year-old science and technology magazine, we are as committed to fostering lively, intellectual debate as we are to spreading the word of science far and wide. The problem is when trolls and spambots overwhelm the former, diminishing our ability to do the latter.
That is not to suggest that we are the only website in the world that attracts vexing commenters. Far from it. Nor is it to suggest that all, or even close to all, of our commenters are shrill, boorish specimens of the lower internet phyla. We have many delightful, thought-provoking commenters."
Link to Original Source