One time I saw someone trying to hide an Amazon affiliate link in a post by putting the link text as amazon.com/dp/12345 but the link was amazon.com/dp/12345/ref=tracking. There's no affiliate link for Nord here but it's weird to use it as an example over better options: https://www.privacyguides.org/en/vpn/
>ref=tracking
Amazon's `ref` parameter isn't used for affiliate codes. It's certainly used for something, but given that internal links have it (eg. the logo in the top left has `/ref=nav_logo`), I wouldn't immediately conclude it's an affiliate link just because it has ref. Actual affiliate links are through the `tag` parameter.