Most readable

Mutable default arguments! It's a feature!

Just as a variant, you don't need the str(binaryNum) and the if statement

Instead you can do:

for num in binaryNum:
total += int(num)

considering a binmary number is only 0s and 1s if its a 0 it will add 0 so you can avoid the if statement

Just saying, based on this ranking system, if a Rank -8 completes a Rank 6 Kata they immediately get to Rank 8.

(of course, this probably won't really be used as a ranking system, but still)

Yeah, I completeled a 4 kyu Kata and only got 1 kyu. It also clearly states it is "worth" 5 honor.