A significant amount of migrations are rejected by the target site, the most problematic being migrations from SO to Programmers.SE. Rejected in this case means the question is closed also on the target site, either for being off-topic or generally not being a good question (NarQ, not constructive, ...).
A failed migration like that is very confusing to the user asking the question in the first place, and also unnecessary work for the moderators of both sites, as they have to coordinate to clear the migration history and delete the migrated question.
I think it would be useful to provide direct feedback on failed migrations. Obviously, a perfect SE citizen would be observant enough to notice when his migrations are rejected often, but I would guess that most users don't closely monitor the state of questions they voted to migrate.
Instead, a rejected migration should either cause a notification in their global inbox, or at least an entry similar to declined flags in their profile.
It could be something like this
You recently voted to migrate [Question X] to [site Y], where it was closed as [close reason]. Please familiarize yourself with [FAQ of target site] to see what kind of questions are on-topic there. Don't migrate low-quality questions, close them directly using the appropriate close reason.
Educating users is the first step, it might be necessary to go further if users consistently migrate bad questions. After a certain number of failed migration to a specific site, the user could also be blocked from migrating there.