Yes, and we used co-ment (a successor tool) to develop MPLv2- see, for example: https://mpl.co-ment.com/text/NMccndsidpP/view/

I will sorely miss the functionality when we next roll out a major policy document here. It isn't always appropriate, but for small refinements to documents (which is a very common use case) it is a much better way to discuss changes than talk pages. [Relatedly, I wouldn't think of it as a "feedback tool", but rather as a discussion and editing tool.]

Luis