Ah - finally I found the balance sheets I was thinking of (some Deutsche Bank stuff from 2009). Turns out I was misremembering; it was equity capital that falls under liabilities, which is counterintuitive to me. Capital is, after all, something I have - but I suppose since it's an investment, it represents something I owe.

And I see capital is shown in the balance sheet in the original post as well - but what struck me as counterintuitive in the original post is representing sales as, effectively, a cash flow towards the customers. If not a fiction, surely you have to grant it's an abstraction.