knocked his post count down by 400 posts
Taking someones post count and changing it is offensive. Using Admin powers to change that is not a wise use of power. You may as well go ahead and change his signature for him, its just as obtrusive.
I was not aware of the history as you put it, so I do understand the frustration the crew must have experienced. But the handling of this situation could have been accomplished better?
If he did not listen to past warnings, then either a ban or setting a mod preview posting would have been more appropriate.
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