@loxjox Zakat is not charity, it is an obligation, this is something that we ought to pay exactly. Therefore it is important we refer to what the Qur'an and Sunnah say on the matter, as explained by our scholars.
Instructing people to pay what they do not owe is not the only opinion, I will find you more scholars if you wish as you don't like the two already mentioned. In fact I expect no scholar will dare say that a Muslim must overpay zakah.
It is due on what has spent 12 months in your pocket. أما ما لم يحل عليه الحول فلا زكاة عليه لزوما
To be GodFearing you must avoid commanding what is not obligatory, it is not about virtue signalling. To make what is not obligatory into an obligatory action is just as big a deal as permitting what is forbidden.
I will therefore write this in block capitals. NO SCHOLAR WILL EVER SAY THAT OVERPAYING ZAKAH IS AN OBLIGATION. If you were taught this it is one method. And it is a method they recommend for it's simplicity and erring on the side of caution. It does not mean there is any kind of consensus that people pay zakah on money that hasn't done a hawl in your pocket.
Now if you decide to overpay, that's up to you. If you want to add 50% sadaqah on top of the 2.5% zakah, all power to you. But God has decreed an obligation that nobody should ever exceed when instructing others.