Windows 10 is good, if you want someone to know every thing you write, view, and don't mind it. I just wouldn't use it if I was a writer of controversial political nature.
If you truly believe that MS has hooks in Windows that lets them/someone monitor your private work, then it would be obvious that actually using or sending that material through cyberspace would get it directly into those same hands, or worse.
So if the controversial writing is meant as a purely private activity, never to be seen by anyone other than the writer, maybe that's a concern. But if you feel that all activity is monitored, then what difference does it make if it's seen earlier, rather than a bit later?