Zephyros
Like anything, that depends. A run-of-the-mill RWS is so cheap and easy to obtain, I don't see it as "sacred" in any way. People use them for art and all sorts of things a Tarot reader would be appalled at. But a Tarot deck is a divination tool only in the hands of a diviner, otherwise it really is just paper and ink.
For example, I've written on two of my decks but feel qualms only about one, my beloved Thoth. It isn't rare at all, but it has been my constant deck for over ten years. I also wrote on my Hermetic, but when it was new and I bought it for that express purpose.
Now, when you're talking about decks that are themselves historic monuments... that's another story.
But it isn't misuse, any more than killing someone with a gun is misuse of a gun (made just to kill people). I think that no action in itself constitutes misuse, there is always a gray area.
