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I don't think there is a solution as of yet. I don't think it would be right to just downvote all his posts from now on to lower it. The community is aware of what he has done and will be more acutely aware if he does it again. I doubt he will though because he knows he will be caught. I think that should be the end of the matter.

What about new people or old people who don't know the story but who do rely on the reputation? Or do most people just wonder what that funny number means?

Not to beat a dead horse, but I do believe that there should be a real downvote firecracker in addition to the nuclear bomb flag. And maybe the flag should automatically (after verification of the infraction) reset the rep score to less than the normal starting point.