An article by Jon Russell at TechCrunch reports that:
Medium has abruptly pulled a feature that allowed publishers to operate paywalls on its platform, leaving some independent media scrambling for alternative options to maintain a crucial source of revenue.
This highlights something I’ve mentioned before. If you hand your content over to a third-party publisher you’re entirely at the whim of their policies, and they can change those policies whenever they choose.
I maintain that it’s always better to publish your own content via your own website. Use third parties to market that content by all means but link back to your own internet property.