This would be quite helpful -- not allowing a cancel of an edit doesn't give you a good feeling about knowing that it will be rejected, and it has to take a search here, far far away from the land of not-meta-siteshas to take a search here, far far away from the land of not-meta-sites to actually realise that it doesn't actually negatively impact your rep in any way.
And if it is approved, that's worse, because you need to go back to the question (if you even remember what it was) to rollback your edit -- and presumably wait for it to be approved/rejected - again.
