>>(btw, if dialog should actually be dialogue, epilog an epilogue, etc... then we better start writing all the words ending with a -gue with a -g or vice versa... so, either vog, seg, leag, dialog, monolog, or vogue, segue, league, dialogue, epilogue, dogue, blogue, smogue, clogue)
>
>FWIW, I use "dialog" for the modal form in an application, and "dialogue" for what's in the movie script.

That's like the fine distinction between disc and disk - and nobody uses disque, because they'd risk the appearance of a pinque guy who'd say "it's actually risque, don't you thinque?".

Thunderbird's spellchecker (set to US English) redlines dialogue, monolog and epilog, while dialog, monologue and epilogue are OK. No logic, just a list of exceptions, aka dictionary.