I use Debian testing / UTF-8 locale.
Yes, this is a problem... but workaround found. Rename all folders and track: ä -> ae, ö -> oe, ü -> ue, ß -> ss.
FLAC tags works fine exept for compilation albums. In random frame artist for album isn't a 'Various Aartists' but some artist from compilation. Currently for this album I see 'Eardrop / Progressive Bunker' (correctly: 'Panzar Produktionz / Progressive Bunker' or 'Various Artists / Progressive Bunker' if 'ALBUMARTIST=Various Artists'). TAG example:
ALBUMARTIST=Panzar Produktionz
ALBUM=Progressive Bunker
ARTIST=Eardrop
COMPILATION=1
CONTACT=http://www.panzarproduktionz.com/
COPYRIGHT=Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License
DATE=2010
DESCRIPTION=PP001/2010,
http://www.panzarproduktionz.com/
GENRE=Electronic
LICENSE=http://creativecommons.org/licenses/by-nc-nd/3.0/
ORGANIZATION=Panzar Produktionz
REPLAYGAIN_REFERENCE_LOUDNESS=89.0 dB
REPLAYGAIN_TRACK_GAIN=-0.40 dB
REPLAYGAIN_TRACK_PEAK=0.59005737
TITLE=THC
TRACKNUMBER=3
TRACKTOTAL=8
ALBUMARTIST=Panzar Produktionz
ALBUM=Progressive Bunker
ARTIST=InYourPhaze; Mantra Flow
COMPILATION=1
CONTACT=http://www.panzarproduktionz.com/
COPYRIGHT=Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License
DATE=2010
DESCRIPTION=PP001/2010,
http://www.panzarproduktionz.com/
GENRE=Electronic
LICENSE=http://creativecommons.org/licenses/by-nc-nd/3.0/
ORGANIZATION=Panzar Produktionz
REPLAYGAIN_REFERENCE_LOUDNESS=89.0 dB
REPLAYGAIN_TRACK_GAIN=-2.11 dB
REPLAYGAIN_TRACK_PEAK=0.51782227
TITLE=By the Base
TRACKNUMBER=7
TRACKTOTAL=8