More Medium, this time concerning the custom domains:
Starting today, we are fast-forwarding this migration by opening up custom domains to everyone and making it quick and painless to transfer.
Custom domains are for publications on Medium, not user profiles. This is a bit like Tumblr, and it’s a lot better than using your publication’s Medium URL. I still recommend hosting your own content, but – again, much like Tumblr, and WordPress.com – this is the second best thing.