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.
No. Fucking NO. It's insane to me that anyone could've lived through the past 10 years and not see how necessary it is to always use the /s tag. There's reasonable evidence that Donald Trump's original campaign never would've even got off the ground if it weren't for people sarcastically supporting him and idiots not realizing it was sarcasm