Opponent allies attacking their hero even during opponent’s turn is an established bug with Coran Darkhand. However, there is another regarding the discard ability.

When Coran is on the field during opponent’s turn and and an opponent’s ally dies from combat damage, a card seem to be discarded from Coran’s owner deck.

This is bizarre. I would have understood if the card was discarded from opponent’s deck as a part of the main bug, but not this way around. It may or may not get sorted along the main bug, so here it is reported.