How does Jack fare against Jester? All those Silvers & Coppers for Jester to hit.
Jester is a tricky kind of attack to think about. To me, the main thing Jester does is gain cards, with the attack being a side-benefit unless you can throne or king it to really throw a lot of junk at your opponents. The "attack" part is hitting coppers or estates to give you junk. Since you trash your estates fast, you're unlikely to actually take any curses, and you can just use Jack to trash them. And coppers? Meh. Off of a Jack opening, you're going for a money deck anyway, so coppers aren't that bad, and you can do a little sifting on them. The biggest impact of the interaction, I think, is that in a deck with a Jack or 2, you're going to have a lot of silver, so his Jester is just going to be gaining him silver for the most part, which is no better than what you're doing with your Jack.
So while it doesn't directly "counter" the "attack" of Jester, I think Jack fares just fine against it. Do you ever really try to "counter" the Jester attack anyway?