Best guess? It’s because they have the permission of the site Viglink is running on. Imagine if you could be sued if you edited an Amazon link on your website to another company. That’s just what this software is doing, except it automates the process. It’s how affiliate links work.
That said, I could have sworn Reddit, when they added Viglink, said that Amazon links would not be affected, due to Amazon not being partnered with Viglink. I know Reddit got a special deal from being such a huge site, but that doesn’t seem like the type of thing they would bother negotiating for.
Also, Musicat: decent adblockers block Viglink scripts. I never run into these problems because I use an adblocker. And Reddit tested adblockers and confirmed that it disables Viglink there, too.
Well, if I recall, that was the deal here too: Viglink would linkify URLs but not rewrite them to favor its own affiliates. And then it changed, possibly with TPTB’s permission, because more money. Reddit has publicly foreclosed the latter possibility, maybe because of how they perceive their membership’s tolerance for that kind of thing. In a tech-savvy community like Reddit, involuntary link rewriting is looked upon as pretty scummy. Evidently, the SDMB community isn’t that savvy. Or that picky. Or matter that much to the forum ownership.
Inconceivable, and frankly not "possible"given the operating rules of Business, which is “control,” in this context of information on and given by the market.
Hence, Amazon. Hence, Viglink.
Even the number of events that don’t happen–say, the redirected book ones–(“when the phone doesn’t ring it’s you” is quantifiable by Amazon.
Or that picky. Or matter that much to the forum ownership.