I’m building a qualitative analysis product called Dovetail that uses ProseMirror as its core editor. Dovetail lets you organise user feedback or research interviews by letting you code the content (tagging fragments of text). e.g.
I recently added automatic sentiment analysis backed by Google Cloud Natural Language.
All of this is done in a real-time collaborative editing environment using ProseMirror’s collab protocol (with our own server implementation). There’s a lot more information about the product on the web site, so check that out if it sounds interesting.