I never got around to implementing Quill (or any of its alternatives) but I do remember reading through the spec documentation some years ago with a vague sense

I never got around to implementing Quill (or any of its alternatives) but I do remember reading through the spec documentation some years ago with a vague sense of tingly pleasure. Sad to hear the final product wasn't so great, but I hope the effort and concepts put into that delta spec gets its due somewhere.