If it's something objective (like grammar), or something where you really feel the structure of the story might benefit, I'd wait until after the reveal and then email the author privately, or even leave a comment, depending. I've had mentions of typos made, and that doesn't bug me in the least, but anything more than that....
Overall, I kind of feel "move along" is the best response, but if it's something objective that's really nagging you, and you're giving it to help the poster become a better writer, delaying that part of your response until after the reveal might be the best strategy.
no subject
If it's something objective (like grammar), or something where you really feel the structure of the story might benefit, I'd wait until after the reveal and then email the author privately, or even leave a comment, depending. I've had mentions of typos made, and that doesn't bug me in the least, but anything more than that....
Overall, I kind of feel "move along" is the best response, but if it's something objective that's really nagging you, and you're giving it to help the poster become a better writer, delaying that part of your response until after the reveal might be the best strategy.