If I understood correctly, you didn't mention the alternative solution of optionally disabling access to metadata on mobile phones (like "Hide counter on mobile"). Would that be an easier solution?
No, that's precisely the problem. It wouldn't do any good just to hide the camera icon. I'd have to hide
the line that it's on. But that line might be shared with a globe or a download icon, so I can't just hide it automatically. And each slide might be different - one might have metadata and no globe or download, but the next slide might have all three. So I can't just tell the CSS to hide the entire line on a mobile - that would hide the other options, as well. And those icons are all CSS "floats," so the line won't just magically collapse if there are no remaining icons on it.
In a non-lightbox skin like Jupiter, I can do things like this with some Javascript, "on the fly," when the slide is shown. But in Neptune, the entire slide display is already being controlled by a
very complex chunk of Javascript (the Floatbox script). I can't safely wade into that to make revisions.