This seems like one of those features that are hard to stumble upon without being told it exsists. Should you, like, add a caveat in sudden death quizzes about it?
what if for like a month, sudden death quizzes had a thing that says “Tip: hold Ctrl to mark incorrect answers!” to help more people notice the feature
What if they don't notice??? Think about. Do you remember much about the interface of the first Sudden Death JetPunk quiz you took? (No, I can't). Maybe the first 10 times or something?
is there a mobile version? maybe a button you can use to toggle?
I like the idea so I'll say that what if, for the very first SD quiz a user takes, they get said message.