@mfowler @jwz

"* top-level post comes with a package of metadata attached to it.
* Comments posted in reply to it are metadata.
* Preview thumbnail images are metadata.
* All of this metadata travels with the post.
* The posting instance is authoritative on what metadata is attached, and when it changes.
* Replying to a post means submitting that reply to the originating instance for consideration for inclusion in said metadata"

This is all how ActivityPub already works.

@mfowler @jwz there are three things that Mastodon doesn't do.

1. It doesn't fetch the canonical collection of replies when showing a thread.
2. It does not send out notifications to recipients of the original post when replies are received.
3. It does not look up OpenGraph link metadata before distribution.

All of which is to say: your suggestions are very valid. Implementation doesn't require major changes to the protocol, and changes to the Mastodon codebase will show results quickly.

@evan @mfowler @jwz It sounds like #1 is there to keep smaller servers whose posts become popular from getting destroyed with too many queries.

It seems like there should be some kind of caching solution to that.