In Assassins Creed 2 why does petruccio need feathers?

Answer 1

as far as i know since he gets hung, you never know. the only thing he tells you about them while he's alive is "it's a secret". you collect them after his death because ezio's mother wants his feathers, probably for personal reasons.

Answer 2

If you find all of the feathers you receive an achievement/trophy.

You also receive a special cape, this one for the Auditore family. It renders you entirely notorious at all times while you wear it. This is useful because you can walk into a city with no notoriety, put on the cape, kill someone, take off the cape, and have no notoriety- the actions are blamed on the cape wearer, whom they don't believe is you.