Soon after the migration to our current multiple-artist system, we added an extra feature to our guess featuring artists code to deal with classical artists entered as featured artists in titles. This used to be the only way these credits could be stored before we actually supported multiple artists, so at the time there were a lot of them that needed to be moved to the artist fields.

Looking through the featured artist reports now, there seems to be almost nothing left that still needs this kind of feature. Since it makes the featuring code more complicated for what is nowadays no good reason anymore, we should remove it.

Classical music data "in the wild" generally does not use featured artists (and the few that do just use them in the same way as non-classical releases), so newly imported releases don't need extra handling at all.