Don’t know what was in the A330 FCOM but other Airbus FBW aircraft had a note explicitly warning against putting objects on or around the sidestick. Also, haven’t read this thread in its entirety but the arm rest was raised or lowered to ensure that the the sidestick could be held comfortably with full and free movement and this was checked on the ground. It was often said that you held the sidestick like your best friend's todger ie rather gingerly and converting pilots were prone to over-controlling. If in doubt, let go often worked!