I'm really waiting for JKR's explanation of the whole 'prank' thing (as promised somewhere along the line--March 4 chat, maybe?) before I pass judgment on it. Of course it was beyond reckless and was no mere prank. It could have been impulsive and ill-thought-out in which case it would be explained one way, or premeditated, in which case we need to look at other things.

RP-Sirius has been asked to explain that one many times. It doesn't ever get easier.