bsterz - 12:31 pm on Apr 4, 2013 (gmt 0)
how they could tell the difference between a buyer and non-buyer on a site caught for selling links is beyond me, but he did take the time to differentiate the two.
Examining the site's back link profile and anchor text ratio/variations should give them a good idea about whether the link is paid or not. Also, examining why the site selling links would link to your for free could be consideration.
[Google is ignoring the linked-to site. They are not penalising the linked-to site.
Matt Cutts said that the link from the seller site will not pass PR and not hurt or help a site that did not pay for a link. He did not say that Google would not issue a penalty on the site buying links.