I would double check to make sure you dont have it set up to some odd function outside of the game that would mess it up, I know I have run into that issue with a few odd keyboard keys or mouse buttons. If thats not the case ` and ~ should work fine. I use both of them with my current set up no without any issues. Best of luck on cracking the case whatever the issue might be.
Beware of the man who works hard to learn something, learns it, and finds himself no wiser than before... He is full of murderous resentment of people who are ignorant without having come by their ignorance the hard way. -Kurt Vonnegut, "Cat's Cradle"
This upset me a bit too, I've always used that as my mount keybind, as well as \ for autorun, which was also unable to be bound (It showed it as registering, but when it was pressed it opened the Customer Service window instead). Shame it was those two, because they're universal buttons for me.
US Keyboard, ` is left of 1 and in the beta it shifted the companion action bar from it's own bar to the left or to the center bar and vice versa.
I didn't try binding it, there just weren't a lot of keybind options IMO so I didn't bother, but that might be why.
(I like binding the "lock/unlock action bar" for when I'm shifting stuff around and didn't see that option. Didn't see Autorun at a glance either, but like I said, I just stopped looking after a bit to play more of it.)
I could also not bind an action button to CTRL+A or CTRL+D.
The game will recognize the keys as bound, and the short-cut text will show on the button. Yet pressing CTRL+D does nothing, and CTRL+A will still toggle Ambient Sound rather than using the ability.
So much this. I've complained about this everywhere I can. I has to be fixed. You need to be able to press down ctrl and move at the same time. Otherwise you can't use your spells on the fly like a shadow for example needs to if he wants to get behind his target. Atm pressing ctrl stops all movement to left and right.