I found the problem glyph '/' within dotum font.

Unfortunately, further test on such font in gnome-terminal showed it has severe
alignment problem which every glyph is frequently overlapping each other. Loaded
with fontforge to check the width of the glyphs, but the width seems correct.

FYI, there is a corresponding bug report at bugzilla:

https://bugzilla.redhat.com/show_bug.cgi?id=450810