The polyps only come out at night (I will post a picture tonight, that particular coral has amazing polyps). I believe it is because the XM 10k's have such a high par. If you look at the coral during the day, you can see the polyps, but they are inside their housings (I know wrong term).
I dont know if the clown picks at the polyps or not. I dont think so. I just think he irritates the corals by sitting on them. In my larger SPS corals it does not matter, as they are deep inside, where the polyps are dying due to shading. He normaly does not sit on a smaller coral, but when I took the pictures it was feeding time, and the fish act crazy.