This post explains it. It's related to Medium's "Highlight" feature, not the ordinary text selection: https://blog.medium.com/introducing-highlights-a4df69e8ed

This post explains it. It's related to Medium's "Highlight" feature, not the ordinary text selection: https://blog.medium.com/introducing-highlights-a4df69e8ed43 https://blog.medium.com/introducing-highlights-a4df69e8ed43