RE: Cock feather
The cock feather originated long before the days of mechanical releases, when arrows were either shot "off the shelf", or from a shoot-around style arrow rest. The cock feather would be positioned to point away from the bow, thereby allowing greater clearance and less kick of the arrow as it passed the shelf. The hen feathers would be more forgiving because they were typically at 120 degrees relative to each other, and would pass by with less interference.
When I switched from shooting with a glove to a mechanical release, I used a "shoot through" prong style arrow rest. I would set my knocks so the cock feather pointed down, thereby allowing the feathers (vanes) to pass between the prongs and clear the rest with minimum contact.
After many years of shooting this setup, I have now switched to the newer "fall away" style rest and a cock feather is no pertinent, because the arrow rest is completely out of the way by the time the feathers reach it, and no contact is made.
One other interesting note on the cock feather positioning... If you look closely at your arrow knock, you'll see a little plastic ridge on one side of it. This ridge is normally positioned to line up with the cock feather. It is commonly used by finger shooters to be able to "feel" the position of the cock feather without ever having to look down at the arrow. If you were stalking game or had a follow up shot opportunity, you could knock an arrow without ever taking your eyes off of the game.
Happy Hunting!