It seems that the release editor will not always change the artist credit properly away from the original.
1. Go to http://musicbrainz.org/release/c5be68bc-6b7f-4cee-a359-7344d4e1e856/edit
2. Click the >> button next to artist.
3. Select everything after "Chris Brayman". Delete it.
4. Click outside the artist select dropdown in hopes of making the release editor aware that this should be a new artist.
5. Hit "Add Artist Credit"
6. Enter "Mark Seibert". Select the correct artist.
Note that the preview shows "Chris BraymanMark Seibert &" instead of "Chris Brayman & Mark Seibert"
7. Hit "Add Artist Credit"
8. Enter "Tom Lewandowski".
9. Click outside the artist select dropdown in hopes of making the release editor aware that this should be a new artist.
Note that Tom Lewandowski is highlighted red as it should be, but the preview shows "Chris BraymanMark Seibert & Tom Lewandowski"
10. Go to "Add Missing Entities"
Add the two new artists.
11. Go to "Edit note"
Note that the Edit Release Artist edit wants to change the release artist to "Chris Brayman, Mark Seibert &". No "Tom Lewandowski".
Note that the "Chris Brayman" part of the artist credit still links to http://musicbrainz.org/artist/39867c21-6e2c-4e06-a424-cc9e765f4621 instead of a new artist.