I've just switched from KDE to lightweight slim+xmonad environment and my fonts are not rendering correctly.
I use DejaVu font family (default for Debian 7.x) which supports all characters I need (Proof: I've looked up these characters in gucharmap + in "konsole" app)
I use rxvt-unicode as terminal, with fonts set in .Xresources. "konsole" app (opened directly in xmonad) shows all characters properly. Both urxvt and konsole are set to use DejaVu Sans.
Even google-chrome behaves strangly. Obviously it uses different font for interface and for webpage, but even when I force DejaVu Sans as webpage font (through CSS), it doesn't help.
Lot of other unicode characters works. The one on screenshot is from Korean hangul -- could it be related to asian fonts?