When an Announce activity in someone's outbox points to a Create activity from another instance, the id values still use the internal server. This means that external servers that use ActivityPub to federate with Mastodon will see duplicate Activities and Posts. The id value should point to the single source for the activity, so towards the source server, not the current instance's local representation of the post.

• I searched or browsed the repo’s other issues to ensure this is not a duplicate.
• This bug happens on a tagged release and not on master (If you're a user, don't worry about this).