When Mind Flayer is on the board, and I have control of an enemy creature, sometimes players (myself or the opponent) board wipe to regain control. However, under the rules of "Destroy all creatures", they are all destroyed simultaneously. However, when Mind Flayer is destroyed, control of the the enemy creature is returned to the opponent.

Under the R.A.W., their creature should also be destroyed. However, the bug causes their creatures to return to their battlefeld instead of dying. For instance, say I play Mind Flayer, and I take their commander. Then, I play Damnation, which destroys all creatures. Under the rules, upon reolution of Damnation, Mind Flayer should go to my graveyard and their commander should go to either their graveyard or command zone. The bug however simply places their commander back on the field. It has occured with various commanders as well, so its not an interaction effect that I don't notice.