"Many worlds" makes this "instantaneous" communication moot, which is why I'm surprised so many physicists are barking up the other tree. In "many worlds" what actually happens when a thing "decoheres" is that the experimenter gets pulled into its superposition. So now instead of a dead-alive cat and one scientist, you've got one dead cat, one alive cat, one sad scientist, one happy scientist. Or from another perspective, a dead-alive cat and a sad-happy scientist - the superposition still exists, but the number of things inside it has increased.

So, "I flip a coin and whichever it comes up, heads or tails, the other entangled coin flipped at the same instant comes up the the opposite, with instantaneous communication" is the wrong view. Rather, the coins are entangled (in the past), and observing them pulls the observers into the entanglement one atom at a time as the informational contagion spreads, so now you have world A, where scientists saw "heads, tails" and world B where the same scientists saw "tails,heads". The scientists got slurped in, but they are simply observing an entanglement that existed and still exists and which was established in the past. Only now they are observing it from inside.

Quantum spooky action "at a distance" is local in "many worlds" and never needs to be faster than light.