For the person who created the thread, it won't be new. For the REST of the staff, it WILL be new.
The problem will be if EVERYONE is editing the same post - they won't get notification if a post they've already viewed is edited.
The way we do stuff like that is that everyone posts stuff like "I think 'this phrase' should be changed to 'something else' - it looks better to me" in their own posts in the thread. When consensus is reached on that phrase, someone incorporates the agreed changes into the "master copy" of the post that's being composed. In theory, the "master copy" is the best version so far. When enough people agree that it's "good enough" the "master copy" post is copied into public view.