Viewport Visibility of "DupliFace Objects"
Turning off the visibility of an original object that is instanced using "DupliFaces" by switching off the "Eye Symbol" in the "Outliner" only switches off the visibility of that object in the "3D Viewport" (including "Render Preview") whereas switching off the "Screen Symbol" (which isn't visible per default) also switches off the visibility of all "Instances":
In my case, I could do the a test rendering with F12 leaving all visibilities switched on witchout having the orignal leaf visible in the rendering but only its instances. The behaviour with "Particle instances seems to be different as I have experienced it with the feathers of Piero being instanced by "Hairs".. Switching off the "Camera Symbol" turned off the visibility of the original feathers as well as their instances.