I had a discussion about this before with a few friends who are involved in the humanities which is that I not only think that it is logically inconsistent to grade people on their thoughts, it may also be unethical, a hindrance to true creativity and spontaneity and an enormous detriment to society.
It really makes no sense to say you want to encourage thinking, but then look over the person’s work to make sure they are doing this correctly.
I think it’s more fair to mark on grammar, spelling and general readability of one’s writing. However, I think marking on content is nonsensical because it hinders genuine freedom of thought. Giving contradictory messages that there is a correct way to be original is extremely damaging to the human psyche, in my opinion.
That’s why you don’t get many true philosophers or artists coming out of formal academia within the humanities, in my opinion.