It will now save the username and date the mark was entered. Also changes done by the children tab will be recorded. Changes done in the regular grading screen will not be recorded. To see the User and Date entered you must go to the children tab and look be grades. It will not show up by Grading.
So this is only a partial solution, but this is as far we will go currently. In order to get full history we would need to re-write the whole grading module.