That's strange. Shouldn't Google be using frequency analysis to determine likely key words? Shouldn't "Disqus" appear so often on high-value sites that Google decides the word is virtually content-free?
Another reason not to use Disqus, in addition to:<p>* Slow load times<p>* Overzealous spam triggers<p>* Poor Twitter/Facebook integration<p>Yes, this is only one user's experience but it's enough to make me stop leaving comments on publishers' websites.