https://github.com/nhn/tui.editor https://github.com/nhn/tui.editor Might be close to what you are after. The only thing I don't think it does is the @mentions

https://github.com/nhn/tui.editor https://github.com/nhn/tui.editor Might be close to what you are after. The only thing I don't think it does is the @mentions, but there is probably a way to address that.