Touchy subject.....
Grades are opinions.
Graders get paid to give opinions, knowledgeable, educated opinions.
It is in their best interest to give the best opinion they can give at the time (not to mention self respect).
You can not guarantee an opinion.
You can not say an opinion is right or wrong. You can only agree or disagree with it.
As grading goes, there is no definitive source to say a grade is right or wrong. If there was, then there would not be a need for TPG's.
The only opinion that matters is the opinion of the one pulling money out of their pocket to either grade a note or buy a graded note.
Just because it says...., does not mean it is.....
That's my opinion......
Disclaimer: I have no graded notes. It has nothing to do with grading. They just don't fit in my little box.