Currently it is often clear to a user that a question really belongs on another site. This is especially true after a comment to that effect is received on the question by another user. Migration by the user however means:
- registering on the other site
- going back to the original site, editing the question, copying the content
- creating another question on the other site
- pasting in the content (which is hopefully still in the clipboard)
- going back to the other site, cancelling the edit and then deleting the question, hoping that no answer has been given.
This is not very obvious, user friendly or efficient. Besides that, in my experience, people don't like to be asked to delete their questions if you hint to them what they should do.
So I would propose that we let users migrate their own unanswered questions instead. Possibly this requires some safeguard, e.g. a trusted user notifying them about the other site. If the user does not exist on the other site the user could be automatically asked to register for the other site as well so that the other site does not have to deal with unregistered users all the time.