I think we are narrowing in on something.
I've looked up other definitions of "commodity" and found this:
"A commodity is a basic good used in commerce that is interchangeable with other goods of the same type."
I like this definition, being both open and clear.
I didn't mean to imply that all phenomena which are systems of behavior not tied to particular groups would defacto be commodities, but I'll think about it more before I fully reject it.
What I meant is that Bitcoin does in fact exist, but not in the sense that water does, and more like in the manner that society and tornados do, as a collective phenomenon of action participants. It is a ledger, rules of engagement, a network of participants, and the unit of exchange within the network, each only existing for and because of the others. The composition of all those things exist for the sake of permissionless, stateless money.
Now, I do believe it to be a commodity. I don't know if it can be justified as the only of its kind, but certainly the first of its kind and only of its class, as all others are imitations or plain copies of it.