Ars Technica: Substack debuts feature that spooked Musk into suppressing Substack tweets. “Today, Substack officially rolled out Notes, the product that creates a feed that allows Substack creators and subscribers to interact. It functions so much like Twitter that it controversially caused Twitter to restrict links to Substack. But Substack doesn’t see Notes as a Twitter rival, telling Ars that Substack has no plans to become the next Twitter.” The way they describe it, it sounds more like RSS.