The first page of navap's original release editor design has a gray background for the fieldset on the left half which has all the inputs. Because some aspects of that information page have been re-used on other edit pages, some other edit pages also have a similar gray background for their input fields (anything with artist credits or guess case).

Although it looked good in the original release editor designs, now that it has migrated to other edit pages it makes musicbrainz look a bit too boxy again (like the old server). I think the border and background for many of those boxes should just be removed. For consistency that probably means most of them should be removed in the release editor as well.