See http://chatlogs.musicbrainz.org/musicbrainz-devel/2012/2012-07/2012-07-03.html#T19-42-16-476930

Pre-NGS, lookups were turned into links with an edit icon when they had an entity assigned. Taking my example from MBS-4529, before we had http://classic.musicbrainz.org/edit/relationship/edit.html?type=url-track&id=1070&returnto=1 and now we have http://beta.musicbrainz.org/edit/relationship/edit?returnto=http%3A%2F%2Fbeta.musicbrainz.org%2Frecording%2F12b182f3-5483-47d9-996e-41498b3b2fde&type1=url&type0=recording&id=1808

Having a permanent search box makes it hard to add links and disambiguation comments, leading to tickets like MBS-3339 and MBS-4529