Hopefully a future set answers that, whether by visiting Chatterfangs home turf or gaining additional insight from flavor text or something
Belle has plenty of Shift-worthy options and ties into several common types (Hero, Princess, and Sorcerer)
Still, I loved being able to attempt to counter a foes spell with Daze (one of the most valuable cards in Nemesis ) by returning a tapped Island to my hand, seeing them smugly pay the they left open, but then pitching that Island and another card to pay the alternate casting for Foil, then watching their face fall - all while being fully tapped out
The only way to outright interfere with them was to play heavy graveyard hate or have removal/hate cards that exiled the target instead of sending it to the graveyard
I didnt think it was remotely possible to make a card that was better than Reflector Mage at the same casting cost, yet we may have one in Spell Queller