Yahoo has several links from SEO sites. They're not talking about Yahoo; I believe they're linking to Yahoo purely for the purpose of getting seen in Web Comments. In this image, I've highlighted the spammy backlinks.
I'm seeing similar results at other popular websites. Web Comments is enabling a new kind of spamvertising. It's a kind of site-specific AdWords campaign except you don't pay for the clicks. It's kind of ironic that Google is the company that created and promoted this extension.