What was Microsoft thinking? Did you actually talk to anyone who uses Word intensively for document editing and drafting, like lawyers? There is a massive community of users who don't do "collaborative" editing, and in fact have to avoid that for most of their documents because they are often dealing with confidential internal communications. So "Post" or "Send" are the worst possible ideas, and they're actually really distressing to even see in a confidential document.
Why would you break the old Word comment model to replace it with this horrible new comment model. I'm adding my vote to literally everyone else's here, with respect to all of the defects of this new model. This breaks workflows which are decades old, and crapifies the product.