I guess you're right. But only if we redefine the term "capital" in defiance of hundreds of years of usage and practice.
Do you expect this kind of "capital" from all businesses you patronize? Do you think you should help decide strategy at McDonald's if you buy an Egg McMuffin?
You can come up with a novel idea like radically defining capital, but that doesn't mean you're correct or that anyone will agree with you.
I don't think it's terribly controversial. Consider two Twitters: the present one, and another devoid of all users and their content. Does one have less value than the other?
We're already engaged in dialog which respects content as capital. Consider Ben Lee (legal counsel to Twitter) who said, "Twitter users own their Tweets." How is it that a tweet is ontologically capable of being owned? Well, it's intellectual property and as such an object capable being owned. Moreoever, it's owned by author, not Twitter. If you answered in the affirmative above, then it's even participating in the circuit of value creation. Yet, the production of tweets contributing to Twitter's value happens largely for free. It's quite simply benefiting on the backs of free labor.
Anticipating your next point, yes, Twitter users willfully choose to participate, but this doesn't negate the process that's taking place. Free labor creates capital.
This process is markedly different from your McDonald's example. It would be akin to people voluntarily supplying McD with beef patties for free. Happy to discuss that though. I'm fairly certain it would be a fruitful discussion.
But, for the sake of argument, let's take your notion of "Free labor creates capital". This implies a one-way exchange/robbery. That is not factual. People use Twitter and are not required to pay for it. This is an app requiring huge costs to build and maintain at scale. Again, they are using it for free. Users are getting the tools for creation and the (mass) distribution of the created objects for free. Moreover, users agree to TOS as part of that. Nowhere in the TOS will you find the notion of "owning your tweet" or being a capital creator/owner.
Again, you're radically redefining terms in a hand wavy, because-this-is-what-I-believe manner while also overlooking the basic facts of the situation and 100s of years of convention. Which is fine. Just don't expect the rest of us to get on board.
I don't think it necessarily implies a one-way trade. Users supply twitter with content-capital(and their time in attention) and in exchange they get the benefit of access to other users and socio-digital engagement. Yes, it's for free - there's no money being exchanged, but it isn't a one-way process by any means.
As far as re-definining terms, you can guess I'm not in agreement. But also know that my analysis isn't some idiosyncratic redefinition. In fact, my analysis sits staunchly after the historical development of Ricardianism, but prior to the marginal revolution. To claim that it isn't based in fact is a nod to the implicit assumption of the orthodoxy of marginal-realism. It's funny. HN will claim that the world could use more heterodox thinkers, but when it's presented with them fiercely holds to orthodoxy.
Do you expect this kind of "capital" from all businesses you patronize? Do you think you should help decide strategy at McDonald's if you buy an Egg McMuffin?
You can come up with a novel idea like radically defining capital, but that doesn't mean you're correct or that anyone will agree with you.