I've always agreed with Ken on this. I can't imagine a mistake so bad that it would warrant using mucked cards for a reshuffle. One of the contributing factors can be directly linked to procedures used by most dealers. These current methods make it almost impossible to clearly identify the "proper card" when a premature action occurs.
Keeping the muck separate from the burn cards would be helpful. I've seen a variety of inconsistent table layouts ,i.e., automated shufflers, some on the left, some on the right. I've seen muck cards placed on the same side (or area) as burn cards. Another "pet peeve" is the method used by dealers when dropping the deck stub at the end of the deal. Fanning the stub, from the burn into the muck is the most common, and the most impractical. The method I prefer, and teach, is simply sliding the cut card from the bottom and drop the stub. Touching the cut card with the ring and middle finger of the left hand, (for right handed dealers). The cut card will practically stick to the fingers and separate the deck from the cut card with ease. Drop the cut card above and between the table tray and you won't have to "fish" for it for the next deal. That's it...no massaging the cards or pushing the cards together in a rapid movement that can only create the possibility of exposure. When done properly, the muck, burncards and deck stub are clearly identifiable and the cut card is in the desired position for the next deal.