This standard seems like a terrible mistake. Isn't this exactly what malware creators want? To condition users to click the browser pop up that says "YOUR COMPUTER IS INFECTED WITH MALWARE, CALL THIS NUMBER/INSTALL THIS HORRIBLE THING TO FIX IT?"
Why on Earth would anyone issue a standard that says that ISPs should deliver that kind of notification, thus training consumers to believe them?
When used by practicing engineers as a low-overhead way to document interoperability requirements for working software, it's been fantastically successful. But it also lends itself to this kind of pseudo-fraud "standardization" by less ethical players.
Bottom line: an "RFC" means nothing per se. What matters is whether the community wants to support it. So RFC7540 is an important standard everyone agrees to support. RFC6108 is garbage.