Not sure that this bug may affect any option though, since there's only one option that has two words in some selections, that is "texture filter". When there's two-words selection made ("linear nearest" for example), space character is substituted by '_' when cursor is not on that option.

This bug is still present in 1.24 and current SVN code. But i've seen that it appears only in Hexen, where the menu items are highlighted with a different colour when selected.

Removed underscores from that option.