And then eventually the paper itself is worth more than the banknote.

I do wonder how a somewhat valuable metal like copper would work here. The copper standard. Go by the weight of the coin times the spot price of copper. Then the govt can’t keep printing more but I gyess they’d have to be on board

I did the back-of-envelope calculation [and now you have to read it :)]:

A slug about 2 inches in diameter, 1/4 inch thick, is worth about 1 USD at today's copper price (weight = 1/4 pound).

So it might almost, but not quite, work as coinage. Maybe in a very poor country populated by body-builders.

Quarter pounder. Yeah maybe it would have to be some kind of a fractional currency. Or some more suitable metal. Silver would work but the price is a bit volatile. There already exists “bullion” silver coins that fit the bill

I think the argument of the article is that the banknotes' value is bounded below by the cost of the paper. If it costs more to print banknotes than they're worth, nobody will print more and as circulating notes wear out you'll get deflation.