From the Europe PMC Blog:
Scientific communication does not stop at the moment of publication. Scientific discussions in the form of post-publication peer review can provide valuable insights for published articles, bring up an alternative research perspective, or even present updates for published research. At Europe PMC it’s part of our mission to support innovation in scientific publishing, and we believe that community feedback constitutes an important part of scholarly communication process. That’s why we are proud to partner with Hypothes.is, a non-profit organisation developing open annotation tools, to display post-publication comments from PubMed Commons on articles in Europe PMC.
We hope that this effort will provide better visibility for scholarly commentaries as an important part of the scholarly record.