Yesterday, I bought Trackmania Turbo. I am enjoying it so far!

I started playing the Solo Campaign. I love how every time you earn a medal, it says how much you climbed in rank on the worldwide and the regional ladder. But after getting at least a gold medal on every white track, I decided to try 'Worldwide Challenges'. I noticed that after earning a medal in a challenge, my rank would climb as well, even though the medals I earn in challenges do not count as 'real' medals.
It doesn't seem fair to me that medals earned at the 'Worldwide Challenges' increase your rank, because this way theoretically it is possible to get an infinite amount of medals. I am curious exactly how the ranking system works and how the medals from the different 'gamemodes' are weighted. Can someone please clarify this to me?
