Going to the Hangul block in gucharmap shows lots of 0000 hex boxes, which is wrong. This has been noticed on systems with fontconfig 2.3.9x, and it has been claimed that it is fixed in fontconfig 2.4.0.
Unfortunately, I'm still seeing 0000 hex boxes for hangul in gucharmap with fontconfig 2.4.0
Fixed upstream: http://bugzilla.gnome.org/show_bug.cgi?id=355605
fix is in 1.14.3-2