That's a false sense of security. We have a LONG list of vulnerabilities in open source software that were "simple" programs for decades. The house of cards approach to security is just not it.
I got the point. I just disagree with the merit of the point.
Microsoft decided that additional complexity for the notepad application is worth the tradeoffs. I tend to agree with them: Notepad is traditionally most heavily used to peruse readme files, which today are primarily written in Markdown. Therefore, having Markdown support as a first-class feature makes good sense.
Furthermore, I point out that it is an optional application that can be uninstalled.
