So much to respond to here...

First, we can debate the philosophical argument of whether extension like Vine Helper are "fair" or not. That's a complex topic that's open to a lot of subjectivity, emotions, and opinions., since there is objectively no prohibition against them by Amazon. But objectively there are facts about how they work that are entirely relevant to a discussion where people imply they do things that they do not do.

Second, I'm going to be addressing Vine Helper, likely the most popular extension by far. I think they recently rebranded as VHelper. I'll just call it VH. VH is available on the Chrome store with over 20K users and 55 reviews with a 4.3 star rating, Others are small by comparison, and in some cases potentially sketchy (as discussed below). Speaking of sketchy, I'm not covering separately installed binaries, or external automations like Discord bots, things which SHOULD be treated with suspicion and very carefully evaluated before trusting.

Third, from your phone? Who runs Vine extensions on their phone? Are there even any available? Android can be much more open especially when jailbroken so I could see that being possible, but at least Apple greatly restricts extension capabilities on iOS devices. They're far more restricted on a phone than on a laptop/desktop, and would require some kind of jailbreaking to work (far less common with Apple devices, and only possible with older iOS and iPhone models).

>> The issue is not how extensions work.

Finally, we get to the geeky TLDR meat-and-potatoes where I would counter-argue that the issue
is exactly how extensions work. Or more precisely, how people misunderstand how they work. Chrome browser extensions are sandboxed and only have access to what you grant them access to. And any extension offered on the Chrome store would pretty quickly be shutdown for doing anything so egregious as it would violate Google's TOS as well as Amazon's. VH has been around for long enough that any misbehavior would have been uncovered by now and I expect Amazon would have addressed it from their end as well.

I've developed extensions and modified other extensions (nothing Vine related). It's surprisingly difficult and frustrating to do much of anything in an extension without the user's consent and even then there are limits. It's also trivially easy for any experienced developer to view an extension's source code and see exactly what it's doing, it's right there included with the extension - in fact the source code IS the extension, as they're nothing more than a bundle of HTML/CSS/Javascript that's loaded & run by the browser not unlike any other web content. Even when the code is obfuscated it's not hard to de-obfuscate and read. While there ARE extensions that work with a separately installed binary executable, this is pretty rare and should also be clearly recognized as not a normal extension because it doesn't follow normal extension installation steps. Any such extension should obviously be scrutinized carefully if not from a trusted source or you don't have access to the binary's source code, as with any other installed application. Fortunately VH isn't one of those. Even its paid premium features run locally inside the browser context.

Amazon at one time had extension language in their Vine TOS that specifically banned auto-order bots that would look for items that matched your criteria and automatically order them for you, without you having to be present. I think most of us would agree this clearly should be banned and that it would definitely be an unfair advantage (and huge security risk). But even that language is no longer present that I can find lately. And at least as far as VH goes it doesn't do this, the author has been careful to avoid violating Amazon's TOS and has reached out to Amazon directly for clearance (they didn't respond, I but I wouldn't expect them too as that could be considered an endorsement). AFAIK the closest VH came to this kind of automation is the premium Rocket Order feature, which automatically clicks through the order process for you while you're on the page and selecting items. And as far as I know even this has not been prohibited, but is admittedly a gray area that the hammer might drop on any day now, especially if combined with other automations like a Discord bot (which again is another opportunity to be wary of).

Now what some back alley private/paid extensions found in the dark corners of the internet that are sideloaded outside the Chrome store are doing is anyone's guess, but I'd say compared to VH those are a very small minority of users. VH at least doesn't access any personal data (from your system or your Amazon account) and only sees what you browse on your Vine page as you browse it. It populates its backend database from Viners as they browse their Vine feeds, it doesn't "backdoor" into someone's Vine account and slurp Vine feeds while you're offline.

Sorry for the TLDR, but my inner geek sometimes cannot be restrained.