I don't think the post I replied to was using refactoring in the strict sense (how do you refactor "as a whole" anyway?) and who said anything about it being a success or used? That wasn't the question.
The post I was replying to was talking about revisiting the ideas behind unix and removing historical cruft. Plan 9 does that (along with adding a lot of new ideas and new features, as to be expected from a research OS)