> the merchant's customers are probably classified as the users. I believe his subdivision of "customers" into "sellers" and "buyers" was to solve that issue -

> the merchant's customers are probably classified as the users. I believe his subdivision of "customers" into "sellers" and "buyers" was to solve that issue - "sellers" are the merchants, and "buyers" and the sellers' customers. It all makes sense to me, but you're right - only in a context where you actually have customers