When merging a release, the merge is only shown under the release artists. Since merging releases also merges the recordings, this means that people can merge recordings on Various Artist releases without anyone subscribed to the track artists knowing. Since recordings can be shared by tens of releases, this makes a single bad merge a complete nightmare to fix.
See http://forums.musicbrainz.org/viewtopic.php?id=3332
and the discussion on http://chatlogs.musicbrainz.org/musicbrainz/2012/2012-01/2012-01-03.html
for a real example. That track alone was linked to about 70 releases before bitmap started fixing it and there are another 15 tracks on the release that need fixing.
I agree with this request, but only if the "merge medium and recordings" strategy has been chosen.
Otherwise it's going to generates huge noise in subscriptions mails, each time a multi disc various artists compilation is merged with the more frequently used "append medium" strategy.
(I already have this issue with "Add medium" edit for VA compilation where I'm subscribed to most artists appearing in the compilation)