This evening I upgraded my workstation from 2015.10.0.2206 to the latest version, 2015.10.0.2208.
After the reboot I see MsMpEng.exe and NisSrv.exe are running now, implying Microsoft's anti-malware solution is on task. I have not seen these running before on this system (but know them well from test systems that don't run Avast) - every version of Avast so far over the past year+ has convinced Windows 8.1 to shut down its own anti-malware software solution.
Anyone else see this? I don't think it should be so.
I'm going to reboot again now, on the theory that Microsoft started theirs up because Avast was in the middle of a software install during bootup and wasn't protecting the system. I'll report on the other side whether the Microsoft Security solution has gone dormant, as it should be, again.
-Noel