I think it may have been sentiment analysis. The low ranked threads appeared to have a more negative tone, at least during my quick anecdotal survey, and this thread was high ranked perhaps because people hadn't had time to create really long complaints.
It can't be sentiment analysis because some items didn't have any comments but still had a percentage. Some other clues that we have is that the percentage didn't correlate with the color and that pretty much all the recently submitted links didn't have percentages.
