"And if there's a moral there, I don't know what it is, save maybe that we should take our goodbyes whenever we can, and that's all."
Below the reply more is a "defense" of one of the aspect of the story, although I'm not defending it too hard, I do believe the story could benefit from second pass. Anyway, spoilers.
I think the fact that Wanda was not allowed to use the moon road was to show that the rules of the magic world are as petty, vile and made up of the subjective whims of powerful people like the rules in our world. That being said, maybe the story could have been clearer on that point, I don't want to defend it to hard. EDIT: Did not remember the character was called "Wenda Mann." That is not one of the decision I defend.