I posted a battle report where I was mis-using Darth Vader and it led to my defeat in my 2nd of 5 games for the day. A user pointed out that my opponent may have known the card effect and didn't mention that I was using it wrong.
After this game, I played round where My Decimator was being chased by another Decimator. We were both down to a few HP left. My opponent took a shot and missed. He stood there in shock that 4 dice came up blank. After a second I reminded him that he had Predator and could reroll. That dice roll led to my defeat next turn. Whereas I probably would have won if he took the "missed" result.
So the question I pose is...Should you remind your opponent of card effects or actions?