If the concern is that someone would favor their own answer over that of someone else, it would seem that that is offset by the fact that the post must have a score of 10 or more.
If the concern is that the user would just copy the content from another post to get the badge, then either the question is a duplicate, or this is impossible, as only the first post that was posted as an answer can get the badge.
Especially with this blog post, it seems that creating a canonical answer is a good thing. Why should the person that created such a thing be precluded from getting the enlightened badge?
As such, I would appreciate an explanation for the current state of things, and also request that it be changed.
Disclaimer: I do stand to get the badge from this post.