Comment #2 on issue 2823 by [email protected]: Patch: Fixes position of mensural c clef
http://code.google.com/p/lilypond/issues/detail?id=2823
Sorry, I omitted mentioning discussing this with Jürgen Reuter (in German), and the _existing_ usage is what matches his manuscripts, namely the middle of the clef being before b! He thinks that the main problem may be that the clef is misnamed as being a C clef when it is more like a double-storied G clef.
He wanted to see whether he can do some more research, but according to his sources, the current behavior is correct, even though he might have mischristened the cled itself.
