The titles are distinguished by how many posts you have. It used to be really dramatic, but I think now if you reach 1,000 you can make your own title (or if you become a mod or instructor). We used to have new titles for every couple hundred posts, where you reach "Grizzled Veteran" - the top!!

The reputation thing is just kind of... odd. I think people can give you certain reputations, with certain comments. I haven't really checked them that much.