Every few weeks there is another user complaining about not being able edit their questions / answers, after the question gets migrated.
The answer to this is always the same: "Associate your accounts".
I think that there should be something on the originating question that tells users to associate their accounts.
This feature could be visible to only people who have asked the question, or have answered that question, or it could always be visible.
This, I hope, will relieve some of the confusion about migrated questions.