Those are basically what dictates how far down the valve cover sits, and in turn how much the gasket is clamped between the cover and the head. The gasket is actually not the standoff. I.e. these are what you file down if you're having leaking issues, so the gasket is clamped tighter. You can see this by putting the cover on without a gasket. But it looks like most of it is there so that shouldn't affect this function. I would be more worried about trying to glue the pieces back and having them fall out into the engine than leaving it the way it is.