All the ratings and stars, groups etc were done by me, they're quite complicated to explain as they all involve multiple variables. These include post count, reputation, length of membership etc.
There are 4 hidden groups which you get promoted to gradually, nearly all of our active members will be in the higher group, while most members (non-active) will be in the lower group(s)
The stars are separte to this and is simply done on post count. There is no particuarly pattern, though you will get to 5 stars by 1000 posts, then the colours change approximately every 500 to 1000 posts there after.
Rankings (bronze, silver etc.) Were an idea i came up with after running out of junior, member, senior - since most of you were in senior i added brozne silver and gold, platinum and diamond to the rankings. If you change your ranking (custom title) you will lose that ranking, although I think you cna get it back by removing your custom title.