Elite means you have a high-quality project in the Elite showcase. Infantryman means you have access to all the boards. Contributor means you have access to write articles for the homepage.
Mods and Admins can change theirs to whatever they want. I could be "Lord Extra Fries" or "The Guy, not the Game or Fanfilm", but then it's kind of hard to tell who's a mod for the new folks.
I would say Elite is a badge of honor because it does mean that you made a really great project.
Infantryman is the only one you can get through post count. It's basically Veteran status.
But it doesn't really mean anything in terms of "I'm better than you because of my massive post count." It's just a little label under the name.