@maegul
I just checked and Mastodon does have a whitelist mode instances can use of they really want control over their data.

"This mode is intended for private use only, such as in academic institutions or internal company networks, as it effectively creates a data silo, which is contrary to Mastodon's mission of decentralization. This setting was known as WHITELIST_MODE prior to 3.1."

https://docs.joinmastodon.org/admin/config/#:~:text=This%20mode%20is%20intended%20for,as%20WHITELIST_MODE%20prior%20to%203.1.

@jbwharris @shlee @snarfed.org @activitypubblueskybridge @fedidevs @fediversenews