I, for one, am glad MS is finally going to start flagging this for correction when typing. As a young-un, I was taught (early '00s) that everything should only be monospaced. Well, sentence structure-wise that is. Line spacing is a different animal.
It's really frustrating to go and make edits to an older document that has double spacing between sentences. Good thing the find&replace tool can fix it all instantly.
Now, if everyone would just agree that we need the Oxford comma, 80% of all my grammatical pet peeves would be solved.