• Open http://musicbrainz.org/release/6ea3465e-180b-4960-a73f-b421dba8d68b/edit
• Go the tracklist tab and switch to the advanced editor
• Click "credits" next to track 1 and notice that it's currently linked to "Kenan Doğulu" with "Ozan Doğulu (feat. Tarkan)" as the artist credit
• Click "Artist as credited on this track" so that you can copy the existing text
• Text vanishes, so you can't copy it (and you can't get it back without retyping it)
• Try to copy it from the preview. The preview updates to say "Kenan Doğulu" so you can't even copy what it said before.

I actually wish it would never delete that field when I click on it. Often the credited name I want to use is a variation of what's already there, not something completely different.