Does the alt+RMB drag work?

That's odd. Is *anything* "copied into" the shader? As in, would connecting a color to Emission and disconnecting everything else make a difference? It could be that you have two shaders with the same name, and only one of them is actually updating.

Possibly, yeah. Perhaps a way to toggle whether or not AO should affect direct light in addition to indirect light

It's not really possible with PBR, but it's possible without PBR, in which case you'd simply multiply the specularity with your mask

You can use specular ambient occlusion to mask out indirect reflections at least, but I presume you want to mask the direct specular reflections?

I presume those aren't recompiled in that case, try reopening them with SF

I'm actually not sure what is causing this, it seems to be Unity related though, not SF:

http://stackoverflow.com/questions/32692193/clip-area-shader-in-unity3d

Though this is definitely a bug that Unity should fix on their end

It's still a bug on dropdown menus on nodes like Dot / Atan / ScreenPos etc

Likely, yes