Used coffee grounds - Toss or reuse?

[Whisky]

Of course. But they were referring to pots.
By the way, my mother used the ground coffee to fertilize her geraniums, in pots. They were so beautiful that people used to come to really admire them and ask what was her secret (which was not a secret because she told everybody it was the coffee).
The geraniums however had problems sleeping at night.

I think that was me that mentioned pots first. I should have explained a little better. We put them in there maybe twice a year, mostly for the nitrogen they provide. I see your point, if we put all out grounds/pucks in the potted plants they would no doubt die from the soil becoming too acidic.