They sell sata cables that come with a 90 degree connector if your worried about it. I don't like the idea of bending them to far if they are not made that way. Kinking a cable could reduce performance i think. You never want to kink a cat 6 lan cable but that is a little different on how they are made. There is also a difference between a bend and a kink. They are designed to bend a little bit.
My advice is if it is working and you are not getting a reduction in performance quit looking at it it will only make you worry more for no reason.