> The salesperson at the grocery store checkout is both human and communicating on behalf of their employer.

I think this is true in the abstract, obviously the people at the checkout are part of the experience of the store, but they're also completely separate from that entity. When I reflect on the cashier at my local store, I don't think of their specific behavior as reflecting on the entire brand. If the cashier messes up the readout of the total, I don't understand that as my local supermarket making a mistake but rather as a specific mistake of a specific person.

That separation disappears if we put the brand up as a facade and don't interact with the person underneath, like we don't with brand accounts on twitter.

This is interesting. I suppose also which position they hold matters. If a chat-based customer service agent was rude to me I would consider this a reflection of company behavior -- but I reached out to someone who is supposed to actually be an active representative of the entity (customer service/technical support).

But the person who turns around an iPad for me to swipe my card may not fit as a "representative of the entity".

I think GP's point is that when you are interacting with Wendy's social media account, you aren't talking to Wendy herself, you are talking to Sheryl the Wendy's Media Associate. Hiding that actual interaction is uncanny.