I put bad luck on someone with Mystical Wyrmhide, and the bad luck effect triggered right as the wyrmhide tried to reflect it back.
What actually happens is that the attachment gets attached and then Mystical Wyrmhide tries to deattach it (and attach it to the opponent). A corollary to this is that you can knock off attachments on the original target even if the effect triggers. This is not consistent with the wording on the card, so I would either change the wording or change when the Mystical Wyrmhide effect is checked.
