I think there is a bit of a communication breakdown here. @todd8 is simply stating that the sphere full of water would be too heavy for this to be a serious pr

I think there is a bit of a communication breakdown here. @todd8 is simply stating that the sphere full of water would be too heavy for this to be a serious proposal. @dghughes is basically replying, "Look, it says so right here. That's their plan." They're not arguing over the material to construct the sphere. It is merely incidental that there was conflicting information in each of their comments.