Why do I get duplicate, empty playlist (linux,easytag,msc) ?

That is bizarre. The only thing I can think of–and it’s a bit of a stretch–is your Fuze was in Auto mode and somehow a copy of the playlist got sent over in MTP…but I wouldn’t think that would persist after a format. I didn’t think MTP in Linux was advanced enough to have proper, behind-the-scenes nautilus integration, but I don’t follow it all that closely, either.