The ability to embed tweets in posts on the online publishing platform Substack has been blocked by Twitter, leaving thousands of users in the dark.

Many do not like Twitter's decision to limit promotion and exposure for tweets including links to Substack postings.

"We're disappointed that Twitter has chosen to restrict writers' ability to share their work. Writers deserve the freedom to share links to Substack or anywhere else," said Chris Best, Hamish McKenzie and Jairaj Seth, the founders of Substack.

"This abrupt change is a reminder of why writers deserve a model that puts them in charge, that rewards great work with money, and that protects the free press and free speech," they added.

The Twitter change has become a huge problem for Substack writers, who use the Elon Musk-run platform to promote their newsletters.

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"It appears that Musk is making decisions based on his own financial interests and petty grievances — even if it makes Twitter objectively worse for users," Judd Legum, author of Popular Information, a politics-focused newsletter, told The Verge.

"If this continues, it's hard to justify continuing to invest my time creating content on Twitter."

According to Substack founders, "writers' livelihoods should not be tied to platforms where they don't own their relationship with their audience, and where the rules can change on a whim".

Musk is a known critic of mainstream media, and recently put a misleading "state-affiliated media" label on NPR's account.

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