Make playlist from all files / selected files currently always creates an M3U file with ASCII encoding which messes things up if any of the included filenames use non-ASCII characters.
What you could do about it is make Mp3Tag automatically create an M3U8 file instead of M3U if any of the filenames/artists/titles include non-ASCII characters.
M3U8 is Unicode version of M3U. It uses UTF-8 encoding (without BOM) and .m3u8 extension. Apart from that their internal structures are exactly the same.