How To Split Artists
This is the operation of creating two Artists where previously there was just one, with some releases going to one of the new artist and the remainder going to the second. MusicBrainz does not provide a specific operation for doing this - instead, you should simply create a new artist (AddArtistEdit), and then move over the releases which belong to the new artist using MoveReleaseEdit.
Occasions where you might want to do this include:
Two completely different artist are "jumbled up" together. This very frequently occurs with similarly or IdenticallyNamedArtists. Note that in the case of artists with identical names, you should add an ArtistComment (ideally to both artists) so that other users can tell the difference between the two.
You wish to associate each release with the correct ArtistName. Many artists use more than one PerformanceName throughout their career, or are simply known by different names in different contexts. You can create more than one artist record for each name, and list each release with the name it was released under. If you're going to do this, please also add PerformanceNameRelationshipType AdvancedRelationships between the artists, so that people can easily browse from one to the other.
Note that there are currently no StyleGuidelines yet that specify which artist should be split exactly how. This is still very new. You might find some documentation on the pages of the respective AdvancedRelationshipType. If in doubt ask on the UsersMailingList.