You should also consider that the average Amazon user is not the average HN user. Even if it was a paid ad, any sort of endorsement from Amazon would certainly "fool" all the middle aged parents out there who can't be arsed to do extensive research on third party reviews.
A rule of thumb for urban shopping is to always ignore "helpful" store recommendations, especially unsolicited ones. They have little interest in doing right by you, and every reason to trick you into a purchase that's better for them and worse for you.
1) Demonstrate trustworthiness
2) Make sure you think of them when making your decision, increasing the chance you'll buy something from them.
Why? Because it's a similar pattern that we see on other websites: the "sponsored" content gets the top spots. The real content comes directly after.
I've had that impression as well. It's not anything particular about the look for me, but that I expect any highlighting / positioning on Amazon to be paid for.
Specifically: Amazon aggressively sells everything else. Why would they not sell promotional placement?
What is surprising that educated people are more aware of marketing/advertising/capitalism?
I only had to see some fake business accounts for large companies(Aldi) acting like real users to put my on high alert for anything on the Internet.