Some releases are credited to "Nick Cave & the Bad Seeds" others are "Nick Cave and the Bad Seeds." This is intentional on the part of the editors and matches the various releases. If you need to group them or normalize them in your own collection, use the %albumartistsort% variable (or something like "$if2(%albumartistsort%,%albumartist%,%artistsort%,%artist%)") in your tagger.
Do not make arbitrary edits to the artist credits unless you can prove that your edit matches the release.
Showing all release groups for various artists. Show only official various artists release groups instead, or show release groups by this artist.