Dear Maintainer,
I found this problem when migrated from Gentoo to Debian.

Debian 8 uses xfce4-session compiled with --disable-legacy-sm by default, so I got some uggly QT applications because of it. Examples: skype, qtconfig.

There's probably something in xfsm-legacy code responsible for qt4/gtk+ themeing integration which is disabled when --disable-legacy-sm switch is used.

The report is submitted to XFCE bugzilla too:
https://bugzilla.xfce.org/show_bug.cgi?id=12012

Thanks for attention.