This is why I quite admire initiatives like Hypothesis[1] where we can annotate the web by overlaying an abstraction on top of it which can give a page more depth and context.
Similar projects like the Genius web annotator[2] tries to achieve the same.
It doesn't mean the commenters (or annotators) will be any less mean, but it certainly is preferable to a Disqus widget dangling on the end of a page, or the default Wordpress commenting engine which allows seemingly anyone to comment regardless of whether they signed up or not.
[1]: http://hypothes.is/