San Francisco, April 10 : Popular subscription newsletter platform Substack on Monday hit back at Twitter for blocking the ability to like or retweet any posts containing the word 'Substack', saying the whole situation is "very frustrating." The company CEO Chris Best responded to Elon Musk with a post on Substack Notes, saying none of his allegations are true and Substack links have been obviously severely throttled on Twitter. "iiiWe have used the Twitter API, for years, to help writers. We believe we're in compliance with the terms, but if they have any specific concerns we would love to know about them. We'd be happy to address any issues," Best responded to Musk. Musk last week denied that he blocked access to embedding tweets in posts on online publishing platform Substack. The Twitter CEO also posted that independent journalist and author Matt Taibbi, famous for releasing Twitter Files, "is/was an employee of Substack". Best denied the claim, saying Taibbi is not and has never been an employee of Substack. "He writes a Substack, and gets paid directly by his readers. That writers making money seems to be such a strange concept is telling. "This is very frustrating. It's one thing to mess with Substack, but quite another to treat writers this way," said Best. Twitter has restricted promotion and visibility for tweets with links to Substack posts -- a move that has not gone well with people. The Twitter change has become a huge problem for Substack writers, who use the Musk-run platform to promote their newsletters. /IANS