>>19
Well, yes. moot's tripcode has been common knowledge for a long time. As far as I know, impersonating the administrator and staff was always a bannable offense. (There was an auto-ban if you posted with the tripcode along side moot's name on the imageboards but I have no idea if this is still in effect.) Even though it may not have been implied in an official manner before, it most definitely is the case now if you refer to global rule #11 on the rules page
[1]
As for people getting away with impersonating moot, unfortunately there are some who slip through the cracks. I'm not going to criticize the moderation done here on 4chan, so I'll leave it at that.
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References:
[1] http://www.4chan.org/rules#global