@silverpill @julian @general account backfilling is issue number THIRTY FOUR in mastodon and has >700 thumbs, >200 comments hemming and hawing about how possible it would be for TEN YEARS.
the solution is just "enumerate the outbox" and it's 200 lines.
like we already have a mechanism for reply controls: the reply collection.
for fine-grained post visibility: access control on the outbox collection.
broadcasting feeds and posts between instances: collections
migrations: collections
store and forward, offline-focused AP: collections
and so on.