Yeah, the single-publication-only thing as far as Medium users with a pre-existing publication is a bit annoying. So far, that hasn’t really been an issue for most folks since they’ve not used Medium for anything (other than me). We could theoretically: A) Setup an account for people to post duplicate stories, B) you could post duplicates on your own account and not add it to your publication.
Not personally sure which would be more preferable; I don’t really link my specific profile anywhere, but it would still look kinda icky. The downside of using a generic account would just be that it’s less drive to a specific person’s profile — though, that said, I think that’s pretty easy to overcome.