No, you're wrong. In general there is not even a concept of "side", but even if there is a positively-curved surface or manifold seen from the other side is sti

No, you're wrong. In general there is not even a concept of "side", but even if there is a positively-curved surface or manifold seen from the other side is still positively-curved. And the same with negative. You can probably convince yourself of this if you think at the triangles mentioned in the article. Their angles do not change even when you change side.