If I had to guess, Sharon, it's so that other users will know it's a reputable link and it's safe for them to open (Assuming that lots of people shop on Amazon), rather than a dodgy link that might have lots of ads or infectious diseases on it.
More than likely it's something written into the code of the site, so it comes up with the
Amazon.co.uk User Recommendation
shortcut, rather than the full link, which would take up a lot of characters (Although 4000 is quite a lot for someone to type), so posters can add their own comments.
We've changed this so hopefully it should now always show as "Amazon.co.uk User Recommendation" rather than the web address, e.g. Amazon.co.uk User Recommendation
It just looks a lot tidier, and yes, hopefully reassures people that it's a safe Amazon link.