I have tried on the snapshot, in a superflat world
EDIT: I have tried without full screen and the anvil doesn't duplicates. Only works with fullscreen mode activated. I'm sure that a little lag while i'm taking the screenshot creates the second anvil
Confirmed! I can see some of blue channel with my glasses. I have taken the photo with my mobile and the glasses
Cannot reproduce. I don't hear these sound :/
Confirmed on snapshot 13w06a