The truths so far, in order of reveal:
Mr. Carnelian
Three players are capable of screwing with the narrative writeups.
I think that this where I got the three witches thing from, on reflection. But, it doesn't actually say anything about witches. This is my least favourite truth so far, because it's so goddamn vague. Honestly, I wouldn't blame you for thinking that this might be a fake rule. Hopefully this one will become clearer after we've seen the first writeup.
Pumpkin
One of the Human Aligned players is actually "Cynical Human Aligned", also known as the "Cynic". They have the goal of a Witch Aligned player and are treated as a Witch Aligned player for everyone else's goals.
This is the most Karifean-sounding rule ever. If you are mafia, props for nailing his style. As for what it means, sounds like they're basically an extra witch, except they might not show up as witch if the cop-equivalent investigates them, assuming of course that the cop-equivalent can only see witch/non-witch alignment.
Formalhaut
When a player dies, they covertly appoint a "Family Alchemist" (taking the title from the previous Alchemist if one exists). The Family Alchemist resolves ties during daytime voting.
I've given my take on this already, but here it is again: Formy's rule sounds to me like if there's a tie, whoever has been appointed the Alchemist gets to PM Karifean to resolve a draw, rather than there being a sudden death. Guess we'll see if it's true if we get a draw and it goes to sudden death rather than being resolved through alchemist ruling.
FFNUT
One Human Player is the Village Idiot. This player will receive a night move but it will always backfire on them.
Sounds plausible. More Karifean-style shenanigans.