Originally Posted by DiapDealer
Sigil doesn't remove the "itunes thing" anymore if it's already present. It ignores it (well, actually it pretends it's in the 'Misc' folder for the duration of the edit, but it's still safe and sound in its proper place after saving the ePub). You just can't currently use Sigil to add or edit the itunes monstrosity.
EDIT: My sincere apologies. I mistakenly assumed the Apple file being discussed was the plist ... com ... xml ... hoobie-whatie necessary for embedded fonts to work in iBooks. I neither know nor care what an iTunesMetadata.plist file is for -- or know what Sigil might do with one when it's encountered.
Thankyou Diap. Helpful as ever...