Behaviour in response to Delete-Actor and Undo-Accept-Follow activities?

[Tamschi]

I'm not entirely clear on how Bridgy Fed handles these activities currently.

If I'm not mistaken, a Delete-Actor at most deactivates the bridge account on Bluesky.
It may be good to instead mark the account as deleted to request purging content from the AppView.

It seems Mastodon at least understands Undo-Accept-Follow, documented here.
I think that too should deactivate the bridge (when received targeting the bridge account's Follow), since otherwise desyncs may occur in terms of deleted notes being visible on Bluesky, if the author's instance doesn't broadcast their Public activity to Bridgy Fed anymore.

[snarfed]

Funny, we've actually moved the opposite way on actor deletes. Up until a week ago, we translated an AP Delete of an actor into a Bluesky #tombstone of the repo, which couldn't be undone. We switched to #account active=false in #1130 to allow it to be undone. I think both flush the repo from the AppView, and re-activating re-fetches it with getRepo etc, but afaik those are implementation details, not strictly specified by the protocol.

If someone removes @[email protected] as a follower, and their instance sends an Undo-Accept-Follow, you're right, we could consider that as also deactivating the bridge. Probably belongs in #1335. I wouldn't expect that to change where Deletes for notes etc are sent though, those should be sent everywhere the original Create was sent.

[Tamschi]

[…], those should be sent everywhere the original Create was sent.

At least Mastodon doesn't track that, no. I'll add this to #1335.

Regarding deactivation and reactivation, it would be interesting to see if Bluesky indeed tries to re-fetch.
(atproto-browser.vercel.app fails to fetch collections for bridge accounts, so it's unclear to me whether that would be possible. I think I read somewhere that Bluesky has a timeout even for account deletions during which they are reversible, but I'm not sure if that's implemented in the PDS, AppView or both.)

[snarfed]

At least Mastodon doesn't track that, no. I'll add this to #1335.

Sigh, that's disappointing. Thanks for the research.

[Tamschi]

For what it's worth, I think no common software tracks per-post reach accurately.
(It'd have to include domains seen in fetch requests too.)

Some may send out Deletes more broadly than Mastodon does, though.
In either case, I think it may be helpful to eventually add a "delete [e.g. Bluesky URL or rkey]" command to remove a specific bridged post.