Charisma / Charm
Wizard, a lot of it just comes from posting more. While you have been a member longer than Ninja you have a little over 400 posts and he has over 5000 posts. It's no surprise that he has a lot more charisma than you. He has a lot more than me as well and I joined before him as well. At the rate he is going within a year he will almost certainly have more charisma than anyone on this site.