FTA: "When that happens, Amazon may take one of several actions. It may block access to the competitor’s site, preventing customers from viewing comparable products from rivals. It might redirect the customer to Amazon’s own site or to other, Amazon-approved sites."

How is blocking and redirecting traffic NOT tampering?

It's standard operating procedure for network filters - redirecting inappropriate content requests to a "this site is not allowed" page.

As long as you're not being deceptive (e.g., inserting your own content, changing other content, changing prices), blocking and redirecting is probably fine.

I think it's reasonable to think "tampering" means surreptitious modification of traffic. If they're up-front about what they're doing then it's just the cost of using their service.

LOL - With all due respect, ANYONE considers "blocking" as tampering.

I disagree. Blocking isn't tampering because you are informed of what happened. And that's moot, in this context, because blocking sites is absolutely legal in the US.

I would think tampering implies more subtle actions.