You haven't explained why "this would be terrible UX", and it would be fairly trivial to add a special "theory" tag or something more general (maybe restricted to high-rep users or mods) to avoid the problem of unwanted decay.
> You haven't explained why "this would be terrible UX"
What's with the tone? I'm not your child
But it's a Q&A site, not a point-gathering exercise. Leave the displayed score of the answers/questions but decay the benefit the author gains from it.