Monospace/proportional is orthogonal to roman/italic; that italic 'true' is still monospace. They do have an oblique variant instead of italic, though.

I have Booleans in italic (blasphemy!) :D and find it is immediately recognizeable that they are spelt correctly when the editor formats them that way. YMMV.

I have no problem with italics. What I object to is one that appears cursive (script) and calls itself a programming font.