First off, it says code was edited in your post simply because it's quite hard to determine whether or not code was actually edited in your code. It may not be in this specific case, but in general it is. There are many minor things in Markdown that could cause something to be rendered as code, or become rendered completely different as code. Trying to pinpoint exactly whether code was added, edited, or removed is way too much effort and would result in too many inaccuracies, and simply determining whether or not something within code was changed between the original and new versions is much simpler, much faster, and less error-prone.
Now, is this information useful? I'm not really sure. I don't really see any direct advantage to telling someone that code in their post was edited, versus just telling them that their post was edited. Chances are a person who would go check on their post from being told it was edited would also check it if they were told, specifically, that code was edited. As well, someone who would not check when told their post was edited probably still wouldn't check if they were told code was edited.
With no real, visible advantage for having this alternate notice, added to the confusion that it sometimes causes, I propose that the alternate message simply be destroyed and that it only notify users that their post was edited, simple as that. If a user really cares enough to know how their post was changed, they'll visit it to find out.