White moves a Queen. Then black moves a Knight. It is now white's turn again. At this instant, for purposes of determining if the white King is in check, black's Joker still moves as a Queen.
That seems consistent. If black would have moved his Joker (as a Queen) instead of the Knight, and this Joker would then have delivered a Queen-like check at the end of this move, it seems logical that you could also use it to deliver a discovered check, by unblocking it with the Knight.
It can still be freely chosen whether the Joker would mimic the last-moved piece of the opponent, or the last-moved piece period. The rules could have been such that the black Knight move switches both Jokers to Knights, instead of just the black one. This is just a different kind of imitator.
All this would only be relevant if you aim a Joker at an uncastled King, which would want to castle on that move. It seems unusua that someone would expose his King this way, so the practical difference might be awfully small.
That seems consistent. If black would have moved his Joker (as a Queen) instead of the Knight, and this Joker would then have delivered a Queen-like check at the end of this move, it seems logical that you could also use it to deliver a discovered check, by unblocking it with the Knight.
It can still be freely chosen whether the Joker would mimic the last-moved piece of the opponent, or the last-moved piece period. The rules could have been such that the black Knight move switches both Jokers to Knights, instead of just the black one. This is just a different kind of imitator.
All this would only be relevant if you aim a Joker at an uncastled King, which would want to castle on that move. It seems unusua that someone would expose his King this way, so the practical difference might be awfully small.