[zerr]

How is it set up? I can't see Amazon ref links in their result page (containing plain Amazon links).

[Cactus2018]

I assume the http referer header?

The claim is directly from the bottom of page - https://help.duckduckgo.com/duckduckgo-help-pages/company/ad...

[ffpip]

When you use an Amazon bang, they add a affiliate link. Not to any search results.

https://duckduckgo.com/bangs