There is possibility of a bit of hunting for badges going on here.
Without checking exactly when the answer was made and when the edit was made...
There are three badges (Explainer, Refiner, and Illuminator) that require an answer and an edit withing twelve (12) hours of each other.
There all are also three badges for editing (Editor, Strunk & White, and Copy Editor) along with two badges for editing older posts (Excavator and Archaeologist)
Finally there are two badges for answering an old question and receiving a certain number of votes (Revival and Necromancer).
What is wrong with that? The site is clearly encouraging this behavior! For a network that wants to be a "Q&A repository" it is certainly a good thing to keep questions and answers as up-to-date, free of errors, and tagged properly.
So what do you do about it?
As was mentioned in the other answer we do have an informal policy of only editing 5 of the top 15 posts by the same user. So while in this particular instance our rule was "broken", it is not against site policy.
IF you must do something...
Typically this is just a user getting a little overzealous and/or having ample free time to hone in on a specific set of questions. IF (big if) a pattern emerges that a single user is doing mass edits over and over again, you can do one of three things:
- leave a comment gently reminding them of the rule
- ping them in chat gently reminding them of rule
- flag for moderator attention so they can gently remind them of the rule
notice the emphasis on gently