Here’s the immediate effect of Threads joining the Fediverse: they’re enabling quote posts. What’s more, they’re be using Misskey-style quote posts.
Which means that the majority of Fediverse accounts will be able to use quote posts.
While Akkoma, Misskey, and Friendica were able to use quote posts, because Mastodon was 70% of the Fediverse, most people couldn’t use quote posts.
Now that quote posts will be accessible to most people on the Fediverse, this is likely to result in a big cultural shift.
https://engineering.fb.com/2024/03/21/networking-traffic/threads-has-entered-the-fediverse/