ProseMirror

We’ve been using ProseMirror for more than a year at Missive - https://missiveapp.com/ We customized it a lot and plugged our own server-side collaborative infrastructure behind it. It was the only editor that offered everything we needed back when we did the research, and I would believe it still is today. Extremely recommended. Also, Marijn is amazingly responsive to issues and pull requests on GitHub.

An incredibly powerful editor. We've been using it for the last year or so at Simpla, and it's been fantastic. It's definitely the most powerful and flexible editor framework I've come across.

very nice. have had many issues with such editors and markdown conversion in particular. this looks like a great script.