For the record, I personally disagree with the idea that it's wrong to simply go 'The artist may cancel for any reason'. It's 'vague', yes, but it's also correct. If I take a commission from you and then don't want to finish it because I've spontaneously decided I hate your face, I should have the right.

Mind, it would be stupid to tell you that and I would refund you in full, but I do have that right. I don't feel like you need to clarify specific reasons why you'd cancel a commission, because that just gives people room to argue with you. "Why are you canceling, I didn't do any of the things you listed in your TOS!".

Of course, this is my personal take on it.