STEPS TO REPRODUCE 1. Open an audio book in the Mac version and paste in a description if the book doesn't already have one. (e.g. Copy paste from Goodreads).
Are you sure that the spaces are really removed and this is not just a duplicate of Bug 432578? As you can read in that report, this is a bug in Qt concerning recent versions of macOS. Can you check if this is fixed when using a build from the KDE Binary Factory https://binary-factory.kde.org/job/Kid3_Nightly_macos/? Could you please also check if this is fixed by the current development version in https://sourceforge.net/projects/kid3/files/kid3/development/, which uses a later version of the Mac SDK and Qt?
*** This bug has been marked as a duplicate of bug 432578 ***