The same kind of loss as caused by using cheap audio cables instead of golden cables perhaps... (sarcasm)
It would make sense to speak about quality loss if it was about FLAC originals but not if the originals are already MP3. You can't save what is not there.
Umm ... no, when you recompress music that was already compressed with a lossy algorithm, you will have lower quality than if you had just stuck with the original. You can’t save what isn’t there, but that doesn’t mean that you can’t lose even more!
This is incorrect. Lossy-to-lossy transcodes always incur a quality loss. It is known