Reply to feature in admin notifiations
When administrator receives notification about placed order there is a customer email listed. However it is impossible to reply to particular customer right from this notification. You have to copy customer email and write a new mail to him.
There would never be a situation when an order notice would be replied to the the store address itself. However, it is common - even normal - to reply to a customer. "Thanks for your order. We are out of green - would Teal meet your needs?"
Rob Ridley commented
Yes! Can't count the number of times I've needed to clarify something with a customer - and accidentally responded to the store. Then sit there wondering why the customer hasn't responded