The split comes just days after Substack announced that it was starting a new service, Substack Notes, that appears to be a Twitter-like platform. “It turns out Twitter is upset about the new Substack Notes feature, which they see as a hostile rival,” Taibbi wrote in a Substack post he titled “The Craziest Friday Ever,” adding: “I’m staying at Substack. On Wednesday, Substack announced that it would be releasing Notes, which looks like Twitter and functions almost identically to it. On Thursday, Substack writers discovered that they were no longer able to embed tweets in their Substack posts. Twitter had been a primary driver of traffic and growth for many large Substack writers, and many independent journalists were left reeling from the news Friday.