Ultimately, short of him picking up enough rejected edits to get edit banned, there is no built in mechanism to slow someone like this down, and since the edit ban algorithm uses the number of approved edits to offset the rejected edits and because he's approaching 100 approved edits today (he would need to get to somewhere in the neighborhood of 35 rejected edits), it is unlikely he'll get enough rejected edits to stop him. This is where the reviewers should be rejecting more posts as too minor.
Normally situations like this as just someone who doesn't know or doesn't understand how our editing process works and how we like things done, and based his response to your (now deleted) comment that you left for him, it seems like his mission is a completely misguided effort to fix something that was fixed in code over 2 years ago.
However, we won't know for sure if that his really his goal or if he is just using it as an excuse to farm rep. Given that his editing mission just started today and he seemed to be doing just fine on reputation on the strength of his own answers until today, I'm willing to given him the benefit of the doubt.
The only thing that gives me pause is the fact that he stopped as soon as he was rep capped, suggesting that he isn't doing it just because he thinks he is helping but also because of the rep reward.
The best suggestion is that we should wait and see if he resume tomorrow and if he does then flag one of the edited posts with a custom flag and explain the situation. A mod will have to deal with him.