Mystery

Amazon.com is known to test every site feature.  Therefore, whenever I see something on Amazon.com I just assume it’s there for a reason.  Today, I noticed something I couldn’t explain and would love to get your feedback.  Here is a screenshot of an Amazon product page.  You will notice some hyperlinks aren’t underlined and others are–

Best practice is to pick one format (underline or no underline) and apply that consistently sitewide so users don’t get confused.  Amazon doesn’t seem to follow this format for this linking strategy, any idea why?