It’s a protocol tussle between the World Wide Web Consortium recommended Activitypub decentralised social media protocol (Mastodon, FireFish, Threads, PixelFed, Wordpress etc) https://www.w3.org/TR/activitypub/ and ATProtocol (Bluesky).

It’s disappointing seeing the attention that is migrating away from Twitter heading to Bluesky, further fragmenting people’s social media graphs when a functioning protocol already exists.