It's to do with your "Trophy Points". If you click on your name/avatar on the top bar it'll show you how many you have. There is more clicking involved to find out how you get them - just hit the number and it should pop up?
I dunno if there is a list of titles you can see, but there is a list of members on the members tab and you can see what their titles are.
I assume somewhere there is an algorithm that governs it, but it might be internal logic rather than user-visible.
The list is: [now we know that Simon hates Munchkin]
I have made it a little slower in terms of advancement, so some people may well have dropped a little.
The management reserve the right to change the title ladder and hidden underlying algorithms at any time, including removing the system.