@paulgc@mastodon.social nope! Replies are only received by your server if they're sent them by the person replying.

On Mastodon this usually takes the form of a mention. When a user is mentioned on Mastodon, they are de facto addressed as well.

In turn, that means the activity is delivered to those addressed users.

If a mastodon user replies to your post but does not mention you, then you will not be receiving that reply. (I think.)

@paulgc@mastodon.social realistically, however, most software is incentivized to actually address replies to the person they are replying to. Otherwise, they wouldn't get it and there wouldn't be any point to replying, right?

@julian wow, ok. That's really helpful - thanks!

@julian@activitypub.space Replying now because I only saw this thread today (h/t @reiver), but I don't think this is quite accurate as written regarding Mastodon.

AIUI, Mastodon decouples replying and notifying. If you reply to a post from a Mastodon server but do not tag the author of the parent post, they will be part of the ActivityPub recipient list (and their server will receive the reply), but if the parent poster is also on a Mastodon server, they will not receive a notification about the reply.

@paulgc

In other words, @paulgc, you should be seeing those Create activities if the reply comes from Mastodon. I think if you reply to a post on your server from https://activitypub.academy you can inspect the payload that gets sent.

@julian@activitypub.space @reiver

@julian@fietkau.social @julian@activitypub.space @reiver Thanks - you're right, I am now seeing them. They turned up at the shared inbox, rather than the user's inbox, which is why I was missing them to start with. activitypub.academy looks useful!

@paulgc@mastodon.social yes, shared inbox is useful to reduce the number of requests sent.

NodeBB will always use a shared inbox if one can be found for the user.

@paulgc Glad it's working! Although now that I've tested it myself, I'm not quite as confident anymore. A test reply I made at https://activitypub.academy/@begusla_laddaciul/115865414668779913 has the ActivityPub `to` set as the account's followers and `cc` to as.Public, but was sent to my server anyway. So I guess the behavior, at least on activitypub.academy, is to not individually address the parent poster, but send them a copy of the post anyway (presumably justified by W3C ActivityPub §7.1.3). Feels a bit funky.

@julian@activitypub.space @reiver

@julian@fietkau.social @paulgc@mastodon.social mm, I don't suppose there's any reason addressees and delivery recipients need align.

You can't enforce it

NodeBB does this too, where we'll send a copy of a reply to everybody in the immediate chain, even if they're not mentioned.

@julian@activitypub.space @paulgc I'm lucky none of my projects so far have needed to really deal with replies, so I haven't had to think about this.

But it reminds me how I've been told that Misskey sends an account's likes to its followers in addition to the author of the liked post, which Mastodon does not. So on Misskey, if a post comes by your feed that someone you follow has previously liked, you see that information. That's cool in some ways and showcases implementation differences in activity delivery.

@julian@fietkau.social that's a great idea! I should adopt that, there's no downside.