"It varies with the number of players in a poor way". It's not just that the size of the Copper pile varies depending on which sets you have, it's that the Copper pile doesn't scale with number of players the way Curses do.
And Jester is not primarily a Copper junker. I don't know why you keep referring to it as such. If Jester always gave the other players a Copper, it would probably be much stronger.
Yeah, I talked about scaling to the number of players. If you own enough coppers that it's infinite, the scaling is consistent (bottomless, Duchy rush happens before coppers possibly run out).
I'm incredibly skeptical that Copper only Jester would be stronger than Jester
Jester is a weak attack because it so unreliable as an attack. You hit mediocre cards and it doesn't really help you or hurt your opponent much at all. When Jester is strong, it is almost never as an
attack; rather, it is as a gainer of engine components. Jester's attack is only strong in conjunction with Spy-type attacks (most notably Scrying Pool) when you can consistently hit VP to distribute Curses. Though even then, it may be preferable to spy for a good card that Jester can then gain.
If Jester were instead a Copper-junking attack, the attack portion would be consistent and reliable, and it would actually
hurt most of the time. You would lose the gaining power of the official Jester, but it would become a better buy on more boards overall.
A while back, Donald wrote about
ways to beat attacks. One of the main ways is that you can "fight fire with fire". Every Curse I give you is a Curse you can't give me. Another way is to simply "set your sights lower". Curses will run out, so you can go for Duchies and then you only need to empty a third pile. But neither of these options are really feasible with Copper junking. The pile is big enough that "fighting fire with fire" just makes every players' deck miserable, and emptying Duchies still leaves you far from a 3-pile ending. Coppers might drain eventually, but not any time soon. And then there's still that third pile.
So no, I don't think Copper junking is suddenly problem-free if you somehow have an unlimited pile of Copper. The scaling may be consistent, but it's still terrible. Can a Copper-junking attack work? Sure. But as I said earlier,
you have to be careful about it.
And as always, if the fan card designer enjoys a certain mechanism and wants to play with it, that's absolutely cool. They can knock themselves out. But when they post it here looking for feedback, the assumption is that they are asking about how the card works in the context of
official Dominion, so "it would work with a hypothetical unlimited pile of Copper" is not a consideration. If people want to make political attacks or reactions that hurt the attacker, they are certainly free to do so, and I have no doubt that some people would really enjoy that. But if they post it here, people can and should point out that such things are problematic.
