Well, that's a strong response haha (infinitely better than no response, of course).

To clarify: the fake community is only for remote actors. How remote actors would follow local users on piefed is up to them. The fake community is mostly for convenience - it's just a place to put content that's consistent with the existing UI.

At the moment, a scenario would be:
andrew@piefed.social wants to follow warsandpeas@mastodon.social, so searches for them and sends a Follow request.
becky@piefed.social wants to follow warsandpeas@mastodon.social, so searches for them and sends a Follow request.
When warsandpeas@mastodon.social makes a post, it's sent to andrew's and becky's shared inbox at piefed.social/inbox
The ActivityPub JSON for his post would only have activitystreams and warandpeas/followers in it.
The challenge is what to do with this. kbin.social solves the problem with having two front pages - one for 'threads', and one for 'microblog'. Lemmy doesn't solve the problem - it just doesn't let you follow users. If piefed were to implement a solution similar to kbin, this would be a big undertaking, and would result in the same '2 front pages' problem.

The alternative scenario I'm proposing.
andrew@piefed.social wants to follow warsandpeas@mastodon.social, so searches for them and sends a Follow request.
After it is sent, a community called piefed.social/c/mastodon_social_users_warandpeas is created.
becky@piefed.social wants to follow warsandpeas@mastodon.social, so searches for them. She is told that a 'follower community' has been set up for them, and so follows that.
For incoming activity from warsandpeas@mastodon.social, if it's not in reply to something, or to a lemmy community, or anything recognisable from 'audience', 'to', or 'cc', the match is made between warsandpeas@mastodon.social and c/mastodon_social_users_warandpeas. The relationship is one-way, and only exists when it needs to. For outside users, 'warsandpeas' would still be a Person on mastodon, and c/mastodon_social_users_warandpeas would be a Group on piefed. The WebFinger and ActivityPub response would be the same as for any other Group. Lemmy users could conceivably subscribe to [!mastodon_social_users_warandpeas@piefed.social](/c/mastodon_social_users_warandpeas@piefed.social), and it would act as a bridge between Mastodon and Lemmy. The Group itself doesn't know which user it is for, but it wouldn't need to: it's just the Group that posts from a particular user would be directed into if there was nowhere else for them to go.
The advantage of 'fake communities' is that they provide part of a consistent UI, with all users posting into a community, so everything can be presented on one front page. Replies from other followers of the remote actor would be added to the post (as inReplyTo would match the id of the post). Comments from subscribers to the local community would reach the remote actor, as they would be in reply to the post's author, and so would be sent in the usual way.

An example of an existing fake community is !tails@lemmon.website. How this works is I have an actor on lemmon.website that subscribes to Mastodon users. I receive their stuff like any other follower, and then Announce it out as if it had been sent to lemmon.website/c/tails/tails. That community is nothing more than a JSON file and a ruby script, but it's enough for other ActivityPub actors to follow, and interact with. An example can be seen at: https://piefed.social/post/71314 (although a better example exists for the same post at https://endlesstalk.org/post/29465340 as this has the author on Mastodon and a user on lemmy responding to each other. Why the piefed.social post doesn't show these is a different problem)

It's fair enough is this all seems too hacky. (I don't think I'm set up for video-conferencing, btw. It's something I'll look into, as I can see the benefit of it)

Just posting to nag you about this: can !tails@lemmon.website be added as an exception to the automod?

It's partly an issue of keys. Every fediverse actor has a private key and a public key. When my instance sends this to fediverse@lemmy.world, it's signed by my private key, and lemmy.world uses my public key to verify it. When fediverse@lemmy.world sends this comment out, it uses it's own private key to sign it. It can't just re-transmit my comment, because it doesn't have my private key. All it can do is Announce that I've made the comment (and sign the Announce).

Mastodon treats Announces as Boosts, so every post/comment is interpreted as a thing that fediverse@lemmy.world has boosted, so you get all these un-connected posts appearing. I think it's mostly up to Mastodon to remedy.

It works better if a Mastodon actor posts into a Lemmy community, then you get the mix like you imagine. e.g.: https://mastodon.world/@Flash/112095241193510662 (this particular post was crowbarred into Lemmy via !tails@lemmon.website, but it would be the same if the author had done it.)

I wish you could, but for all intents and purposes Lemmy and Mastodon aren't part of the same fediverse. Kbin/Mbin let you follow accounts, and I think !tails@lemmon.website automatically turns toots from some accounts (including Takei's) into Lemmy posts.

From Lemmy you can see the accounts, but usually not their content (see note below). @lowqualityfacts@mstdn.social
@georgetakei@universeodon.com

Interaction between Lemmy and Mastodon doesn't work well because the two services structure their content differently. Lemmy is community based and Mastodon is user based. Lemmy doesn't have a mechanism to follow an individual user, and Mastodon doesn't have an analog to communities (afaik).

(Note: In the case of these two accounts, some of their toots are visible because they have been pulled into the !tails@lemmon.website community as part of an experiment to bridge Lemmy and Mastodon.)

(sorry to intrude). This has had a few cross-posts on Lemmy. The link that goes to !tails@lemmon.website is attributed to the author of the image, so you can reply to them via that community if you wish.

(sorry to intrude). This has had a few cross-posts on Lemmy - this one technically wasn't, but it seems Lemmy has picked up on it. If you want some ALT text, and to reply to author of this image, the link that goes to !tails@lemmon.website provides that.

Hello. My community !tails@lemmon.website is getting caught by this. It posts stuff from Mastodon users, so they won't have any karma. I've been trying to figure out why posts to programming.dev have been hit or miss, and the answer of course is that the missing posts are sat in modlog!

If poss, can tails be added as an exception? It's me that's deciding whether a post is made or not, so no spam or weird stuff will ever get sent.

Thanks.

lemmy.world has the community, and is keeping up to date with it, because someone (me, actually) brought it through and subscribed.

midwest.social has the community, but won't get further updates because no-one subscribed (so technically I don't have the inbox address for it - it'll be the same format as everyone else of course, but it would reject updates with the 'community has no subscribers' error if I sent stuff to it anyway).

justworks was in the same situation as midwest.social, but it has a subscriber now, so now it has everything and will keep up to date. I didn't have to do anything - the new subscriber's action re-fetched the outbox (discussed below) and luckily that contained everything that was missing. The post from infosec.exchange is there too, so that wasn't affected by federation blocks.

lemmon.website isn't running lemmy - the tails community is 'virtual' in that it's just a bunch of static files pretending to be a real community. The main address 403s 'cos thats just a folder.

infosec.pub doesn't have the community most likely because no-one who is logged in there has searched for it (instances won't search outside their own database if the query isn't from a logged-in user). lemmon.website is in their /instances list though, so there's no blocking.

1. An outbox on lemmy contains the last 20 or so original Announces that the main community uses to tell the communities on other instances about a new post. To illustrate:
   curl --header 'accept: application/json' https://lemmy.world/c/microblogmemes/outbox | jq .orderedItems[0] would be for the most recent post on microblogmemes. (Op's post is at orderedItems[6]).
   Fetching this allows a new instance to re-create recent posts, as if it had received them at the time.

2. Someone clicked !tails@lemmon.website, but didn't go further (they probably got lemmy's misleading error screen and gave up). As with midwest.social - no subscribers = no more updates.

3. Yeah, lemmon.website is mine. Not running lemmy means I fudge things a bit (including having posts from Mastodon users, of course)

What's happened for you there isn't a problem for screenshots to really fix - it's whatever frontend you're using not giving lemmy's backend enough time to fetch a remote community. This happens loads - I even made a little video about it the other day: https://lemmy.dbzer0.com/post/13703060

When you clicked on !tails@lemmon.website, it did actually go through to dbzer0, and Voyager has no trouble with the community once it's though. A little ironically perhaps, but here's a hastily combined screenshot showing it at dbzer0 and on Voyager:

edit: and the link to the post of course: https://lemmy.dbzer0.com/post/13850191

Screenshotting a post from another fediverse app seems a bit crazy. As an alternative, this post is available natively in lemmy, as text and from the original author (so you can reply to him if you'd like).

I can't give a universal link to a post obviously, but if you're on lemmy.world, it's here: https://lemmy.world/post/11631169, and if you're not, it's available on the !tails@lemmon.website community.

Fun fact: War and Peas is on Mastodon and through ActivityPub magic their posts now also show up in !tails@lemmon.website

Pro tip if you write !tails@lemmon.website without explicitly making it a hyperlink Lemmy will do it for you, and as a bonus the link it makes works on mobile

This was cross-posted from a lemmy community (!tails@lemmon.website) that's sort-of bridging lemmy and mastodon. If you're on lemmy.world, they'll already be a post you can visit, to upvote and respond to the original author of the comic, if you wish. If you're not on an instance that's brought !tails@lemmon.website in yet, it can be done so in the usual way, of course.

(edit: just tried this on a different instance. lemmy being lemmy means you might have to refresh a couple of times after clicking the ! link, but that's nothing unusual)