It hides the other layers and lay folders visibility here. Does this do anything on OSX, or nothing at all? If the latter, is Shift+Click used by OSX itself?

I confirm, same behavior here on Mac Os X. 

Shift+click should work in the same way as we are used it works, but also inside layer folders. 
I like that feature so much, because so fast and efficient.

I don't understand what you are telling me - can you try to describe the actual and the expected behaviour in more detail, please?

No problem. We know that shift+click hides/unhides layers, its a toggle. 
I'd welcome if the same feature would work for layers inside layer folders. At the moment, Shift+click acts on the layers outside layer folders. Sincerely, it makes no sense for me. If i work inside layer folders, I'm not interested of the layers outside. Its simple: Shift+click should hide/unhide only layers inside a layer folder, when we are inside a layer folder.

I've adjusted the summary of the bug accordingly, and set it as enhancement.

It simply doesn't work inside layer folders at all and acts as if the
folder itself was shift-clicked, that's clearly broken.

However I don't see why a fixed version should work any different
than shift-click on a toplevel layer, it should simply make the clicked
layer the only visible layer in the image. Is that what you mean?

Personally, i see two ways to use this shortcut:

A) inside layer folders: hide/unhide layers in the current layer folder only, dont affect outside layers
B) outside layer folders: hide/unhide all layers, and layer folders, but not the content of layer folders

i can try to re-formulate my previous post, where i described in detail what i expect from the hide/unhide layers feature, if you wish

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