Control: tags ! +moreinfo If I got this correctly, you've got some ID3v1 tags generated on Windows, using a non-standard locale depending upon your Windows environment, that qmmp cannot show.
Where should qmmp get the missing information (the locale on the Windows host at that time) get from? Do you think it would be feasible to convert the ID3 tags to ID3v2 and Unicode using tools like id3v2? Please Make a backup of your mp3 files first.