As far as negating mafia hits go, it's a game-to-game thing, which depends on the host. Typically, if the godfather has something special about him, for example, if he automatically appears as a townie, when he dies, the hit's lost that night, I believe. Whenever the godfather doesn't have that specific ability, it's a toss-up for the host to choose.
Anyways, now that GP's dead, I can say this:
I can't believe I was voted out the same day I was "verified" by the investigator! Sure, my results turned out incorrect with that, but still, no one brought up the whole mafia ability to manipulate investigation results, and I still died! It led me to believe that had this been a normal game, and I were actually a "verified" townie, I'd have been killed, too, which is definitely crazy...
Anyways, the game's still going. We'll see what happens now.