http://en.wikipedia.org/wiki/Language_input_keys The button on the Japanese keyboard labelled 無変換 seems to do nothing with ibus-anthy. It is supposed to force non-conversion of a particular word. ibus-0.1.1.20090203-1.fc10.x86_64 ibus-anthy-0.1.1.20090203-1.fc10.x86_64
Muhenkan only needs to work in preedit btw - I don't think reverse conversion is expected. Here is an input example: Ctrl-Space => anthy a s a => あさ (pre-edit) Henkan => 朝 (pre-edit) Muhenkan => あさ (pre-edit) Additionally, further presses of Muhenkan rotate through: hiragana, katakana, narrow katakana, double-width alpha, single-width ascii.
Fixed in ibus-anthy-1_1_0_20090402-1_fc11