The way I interpret the rules, cancel abilities cannot cancel other cancel abilities. (For example, if you Voice of Honor event X, I cannot respond with Forged Edict to allow event X to resolve). Correct?

No reason why you couldn't? What makes you think that it shouldn't work?

Forged Edict and Voice of Honor both interrupt playing an event, and are events. So when you play them, you create a new window to interrupt.