Actually a 0 only has more mathematical effect on the score if the character's score to that point is above a 5. If it's below a 5 the 10 will alter the score more.
Which happens pretty much every time because I can only assume people's perceptions on ratings are skewed by the American grading system.
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I tried to have a fierce rivalry with SuperNiceDog, but he made me look worse than a GameFAQs Contest!