Similar to the movie energy replenish, a button that asks "Are you sure you want to use 'X' diamonds?" with yes or no confirmation buttons.
i'm getting tired of having diamonds used when i accidentally click on the wrong button or my mouse lags a second scrolling to the right button but clicks on the wrong one. i just wasted 50 diamonds to refill my mission energy when i could have spent notes instead.
i'm positive i'm not the only one this happens to and would be very appreciative of having a confirm screen pop up.