Just commit, no matter the response. Adding /s is akin to explaining a joke after you tell it. If someone doesn’t understand or pick up on the sarcasm, it’s not your responsibility to spell it out for them. You add /s because you don’t want to be held accountable.
I’ve noticed people often have completely different answers to the question of who bears the greater responsibility for successful communication (listener or speaker). I’ll add this one to my file.