Just 4 days after writing Windows Firewall dangers - Is your Windows  PC's networking broken after you joined a domain?, I did my first Windows upgrade (from Windows 7). And noticed that Windows Firewall had been completely re-enabled, as well as the warnings telling you that Windows Firewall is disabled.
Not even a year later, that same PC was hit by Windows 10 Anniversary Update, which caused the very same issues. But I finally understood what happened this time. When Windows upgrades, it assumes it knows better than the administrator and re-enables warnings about the Windows Firewall being disables, which causes a notification to appear in the notification pane. The administrator who does not know by heart how to re-disable warnings might click that notification hoping to be offered to get rid of these. Unfortunately, the only visible effect of clicking that notification is that the notification disappears. But that is not the only effect. When that notification receives a single click, Windows re-enables the firewall, without providing any feedback to that effect. Brilliant deceptiveness!
Oh, Microsoft. How could we earn such a direct ticket to Heaven if it wasn't for enduring you and your silly tricks? I'll refrain from explaining how pitiful the upgrade to Windows 10 and then Windows 10 Anniversary Update was until I find an answer to that question.