Joseph, you are right that 0.5/1 really ought to change to 1.0/2 if you regrade. However, because of the way this data is stored in the database, it is almost impossible to fix at the moment. Please file a bug in the tracker. I am currently collecting evidence to justify some changes I want to make 
Quiz
What happens with a regrade to manually changed marks?
Eztabaida hau blokeatu da eta beraz aurrerantzean ezingo duzu bertan erantzun.