Originally Posted by
freecia
Please don't. This will not have the effect you're thinking. It comes off very patronizing and probably sexist in current American culture. I'm fairly sure the emoji was sarcastic.
Absolutely no one in a grumpy mood wants to be told to smile, much less by a customer who simply wants pseudo-cheerful service.
As the person who posted the suggestion to tell the grumpy person to smile, I can assure you that the emoji definitely was sarcastic, for exactly the reasons outlined here.