I discovered a bug regarding the new "Rename artist credits" feature. What I did was this:

• rename "...And You Will Know Us by the Trail of Dead" to "...And You Will Know Us by the Trail of Dead" (converting the three dots to an ellipsis) in edit #16125476, selecting both available ACs "...And You Will Know Us by the Trail of Dead" and "...And You Will Know Us by The Trail of Dead" (capitalized "The").
• this results in a correct edit #16125478 for the former AC, but an incorrect edit #16125477 for the later one (nothing seems to be changed).

Since I can't approve the "Edit artist credits" edits on the main server, I tried to approve them on the official test server and a local test server (running production code), and to my surprise approving the second edit even resulted in an ISE. To see it, try to click "Accept edit" on edit #16084617 on the test server:

Caught exception in MusicBrainz::Server::Controller::Test->accept_edit "Failed query:
	'DELETE FROM artist_credit
         WHERE id = ?'
	(831673)
DBD::Pg::st execute failed: ERROR:  update or delete on table "artist_credit" violates foreign key constraint "recording_fk_artist_credit" on table "recording"
DETAIL:  Key (id)=(831673) is still referenced from table "recording". at /home/musicbrainz/musicbrainz-server/script/../lib/Sql.pm line 103.