[librexpr]

I wish people wouldn't spread rumors like this. ActivityPub does have shared inboxes[0] and Mastodon does use them[1], so no duplicate messages will be sent in your example.

[0] https://www.w3.org/TR/activitypub/#x7-1-3-shared-inbox-deliv...

[1] https://github.com/mastodon/mastodon/blob/a5a00d7f7adff5e0af...