Well, if you never engrave it, it’s definitely going to be useless. It seems like there are enough removers available from events, and that new codes come out slowly enough, that unless you put them in really weird places, you shouldn’t need to remove them very often. Just put them on servants you like, and you’ll be fine.
Again, the codes make so little difference, you may as well just put them somewhere to get some value out of them. The opportunity cost is about as low as it gets. Very few codes have any special use cases, and those are pretty obvious (the debuff cleanse code for self-stunning servants, the poison code for Robin, etc.)