When you look at the original code I feel for the poor coder!
When you're dealing with a project of this size, there is no single "poor coder". Most, if not all of the code has been touched on by multiple people.
A really good bug fix that should mean AI's fight better wars.
I think you're vastly overestimating the impact of this particular bug. The only impact fixing it will have is that the AI will give a slight preference increase to defending a captured Holy City. With a maximum of 7 Holy Cities out there, AIs that don't tend to capture cities frequently, and the minimal nature of the defensive increase, I don't expect anyone will really notice any tangible difference in their typical gameplay.
That's not in any way taking away from the kudos for spotting this bug, but I don't want people getting any ideas that fixing this is going to have a major impact on AI performance - it's not.
Bh