Again, logging my keystrokes in a single text input field is vastly different from logging all of my keystrokes across the board.

Except logging your keystrokes across the board is not what Microsoft is doing. Do you realize how absolutely useless that data would be? They are monitoring search queries, specifically in Cortana. They probably do the same for auto correct instances. They aren't logging all of your keystrokes.

For a lot of people, Facebook is the board.

If you're on Facebook, then I think it's reasonable to assume that Facebook is recording what you do on Facebook.

If you use Windows, I don't think it's reasonable to assume that Microsoft is downloading your browsing history and keystrokes.