The recommendation to grade on specific criteria fits with my experience teaching graphics at a college. With a specific grading rubric, grade challenges can be discussed calmly and specifically. Basically, if I follow the rubric, it's my backup in case of a challenge. "You did this well, but you needed to work on this."
I was never challenged, but that may have been because the rubric (expectations) was given to the student along with the assignment, and with the grade after marking. No "black box" here.
Now, this does limit my flexibility. In a dojo, I may think twice about such a tight rubric. "Character" (for example) might be hard to include on a MA rubric, and it might be an important criteria for grading, so YMMV.
We don't find it all that difficult to include. Are you disrespectful of others, or are you doing your best to support and encourage others? Did you get a DUI, or suspended for bullying some kid at school? Do you spar with an appropriate level of control or are you trying to decapitate someone? Do you show respect for your sparring partner, or do you talk smack?
It's not as cut and dried as other criteria, but it doesn't really need to be.