Yes, nulling is allowed. But i'd advise you not to use it because it will make your strafes go bad and you'll be a washed up player just like me.
Essentially null makes it so when you press any key, it also cancels out holding any other key. So the string for pressing A (left) doesn't just do +moveleft, it also does -moveright, so you would have to press your D key to move right again
