I have yet to encounter this conundrum. I obey Thier's law, and only spend sats when nothing else is accepted. When that is the case, I'm pretty sure the receiver keeps them (or at least that I've used the sats very well). When it's not the case, I do my very best to obey Gresham's law, and dump my bad money first. The only exception is when I'm influencing - meaning that I pay extra for spending sats to make an observable statement to potentially swayable audiences. And then there is not much focus on what the seller does with the sats after the transaction.