This is a good limit to add for this hypothetical system as well. Not only would you not be able to link two points remotely close to each other, you could only go back in time so far.
If you go too far, (run the expansion of the universe backwards in your head) eventually both points would co-exist in the observable universe of the earlier point, thus allowing photons and information to travel through standard space to the later point.
This is fun.
ETA: (Also, you wouldn’t have to be literally fully over the actual horizon of the observable universe from each other. The light we’re seeing from plenty of stuff close to that horizon left its source many billions of years ago when both points were much closer. Most of the currently observable universe isn’t causally linked in the present moment. Like, there are plenty of points in our observable universe, if you directed a radio broadcast in their direction, it would never arrive. This horizon is called the Hubble Horizon and is only 14.5 billion lightyears away in all directions as opposed the 46.5 billion lightyears needed to reach the actual edge of the observable universe.)
ETAx2:(Even more fun is doing the math. If you plug 46.5 billion lightyears into the volume formula of a sphere, you get 421.160 trillion cubic lightyears. If you plug 14.5 billion lightyears into the volume formula of a sphere, you get 12.77 trillion cubic lightyears. If you divide the latter by the former, you get 0.0303 or 3.03%. That means only 3% of the observable universe is within the Hubble Horizon. Another way to say this is that 97% of the observable universe is utterly unreachable, even at the speed of light. Nothing that happens here will ever effect them for all eternity. Isn’t math fun?)