The description does not mention that, when the user reaches rank 8, progress must be 0. It says "A user cannot progress beyond rank 8", which I interpreted as it can not rank above 8, but I think it is unclead if progress should be still counted or not.

Hi. The kata says that if all the characters are repeated the program should return '' or None. However, returning None fails various tests. The description should be changed.

You could just check if both division remainders and return False in that case, since the only True condition is when they are different.