I've completed the first four missions of the game, achieving ratings of either Shadow, Specialist, or Silent Assassin on each. My scores are still there on the leaderboards, but the ratings have been reset to Agent, and the individual scores for each chapter of a mission are now 0.

This might have been only when I happened to notice, but I'm pretty sure this issue was caused when I went back to replay the scored section of the intro/tutorial mission on Purist difficulty (from level select, not the "new game" option on the main menu).

So what's up with this? Did it really reset my scores because I went to replay a mission, as if I were starting a new playthrough and would enjoy having all my records erased? Or is this is a bug? Either way, it's pretty annoying.

Some pics of what I'm talking about:

I figured out what was going on. It has to do with switching difficulties. The ratings and chapter scores are specific to the difficulty that you last played a mission on, but the high scores are cross-difficulty.

It would probably be less confusing if the mission select menus just showed you scores and ratings for all difficulties rather than just choosing the most recently played and then not explaining that. Kinda weird that it seems like you need to enter and exit a mission if you want to see your scores and ratings for a different difficulty.