I just checked a couple of my other Win10 machines and then downloaded a few older versions of the IDE to test.
Looks like all versions of the IDE since 1.6.11 are suddenly having this problem... 1.6.11 continues to properly enumerate all the COM ports, but any newer version has suddenly stopped working!
I would chalk this up to some Microsoft update nonsense, but other folks (in this thread) are also reporting this same behavior on Linux platforms as well.