The practice is only rarely encountered, because it requires that the perpetrator recognize the inappropriate nature of their behavior and take affirmative advance actions to mask it. Most people who have sufficient control and discernment to pull this off are unlikely to be sources of trouble in the first place.
It differs from the typical SockPuppet pattern in that the "Good Me" and "Bad Me" personae do not interact.
Are they being used in entirely different communities? Or is it that they do not interact within that community?
I think back to the newsgroups. misc.rural had, at one time, a poster called "Hopelessly Midwestern" who started many a flame war, usually by posting fringe, libertarian material written by others and then defending it. He would periodically clean up his act, and post reasonable material. And sometimes, he would post personal attacks, really rather juvenile stuff, calling names and so forth. This he would do under a different pseudonym (Bad Me). Upon close examination, the nntp headers would reveal the authorship. Usually though, the pseudonym changed each time to evade killfiles, so did not have the SerialIdentity implicit in a "BadMe?" pattern.
There are parallels with BDSM pseudonyms, for example. The Good me/Bad me pattern can't really work in any MeatSpace encounter because people are recognized. Perhaps that is one reason why the BDSM culture makes some use of masks and similar obscuring devices, aside from the purely fetishistic side.
This could also be compared to Dr Jeckill and Mr Hyde - except that here the user is in control of the identity changes. Maybe it's more like the evil baddies in batman stories and suchlike, people that have a normal identity and an evil insanely criminal identity. There is some kind of a parallell in MeatSpace, though I can't say if fiction worlds count as MeatSpace ...
Maybe GoodMeBadMe behaviour should be encouraged, as it can be a test of the resistance of the system. And if long-time users that create an extra identity to go on a rampage can't disrupt the system, who can ? (Ok, now I realise this was a bit redundant with SockPuppet so deleted some of what I wrote) -- EmileKroeger