You're right about the possibility that his hidden ability could counterbalance his role, but I really do not think that his claim is all that trustworthy, and the fact he went to kill Phoenicks and only he died is a bit strange. The mafia kill not going through N1 seems really unlikely to me.
@Neon Borealis; If we suggested that you killed somebody to prove your role, would you do it?
As for the Trixie thing, her entire role -- including hidden ability -- was revealed. Unless there is a hidden hidden ability (vury unliekli), I'd say that Feliciano just wanted Trixie to be on the side of the town, which would explain the 'somehow' -- like that Autumnbreeze and Enero game, where they were just like "IGNORE THE FACT THAT SPIKE IS IN LOVE WITH FLUTTERSHY; SPIKE AND TWILIGHT SPARKLE ARE LOVERS".