well yeah, but neither Mastodon nor Pleroma currently offer that feature themselves.

I think having parity between all the major platforms could be a huge benefit for the network as a whole.

this question comes up every so often.

Hashtags are great, but they're really just a type of index containing a specific type of topic. They have no notion of membership, and the index itself only contains posts that your instance is aware of.

The local instance timeline is useful if you have an instance that revolves around a certain topic or theme, but it's really just for checking out what's going on in your local instance. For large instances, or instances that have more than one topical theme in their community, this isn't useful for group communication.

Where groups ultimately differ is this: basically, it is a subscription relay that announces all posts that are addressed to it. Every member of the group receives every post addressed to the group. This differs from hashtags because you have a chance of missing posts that your instance doesn't know about, and you usually have a member that can administer group membership for moderation purposes.

Good description.

Another question: What do you think would be a good way of implementing groups within the framework of, say, #Mastodon?

I'd think it could be something like a USENET group, except new posts are pushed to the timelines of users that follow them instead of making users go to the group. And a group's content might only get downloaded to an instance when someone on that instance is following it. #fediverseGroups

some prior art exists for this already: GNU Social, Friendica, and Hubzilla all support federated groups. I believe Zap might as well.

Historically, interaction works like so: instead of a hashtag for #topic, or @ for @mention, you would instead use a bangtag for !group. The bangtag effectively works like a mention, but is specifically scoped to the groups you're a part of. When you type the bangtag, you can only see potential groups to mention that you yourself are a part of.

A proposed ActivityPub version of groups models the OStatus ones: members of the group mention said group when they want to make a group-specific status. Once the status is made, the group Actor Announces it, effectively relaying the status to all participants.

I suppose one stumbling block to figure out involves privacy scoping. People posting to groups may want only the group members to see the status, and no one else. Friendica and Hubzilla have effectively figured this out, but their privacy settings are Access Control based, and much more granular than what other fediverse platforms currently provide.

That's an interesting question: What would happen if someone posted to a group on Friendica or Hubzilla with the expectation that no one would see their post outside of the group, but then it got reposted to Mastodon where someone made a reply that was then available to the public.

if a group is closed/private, no one outside the group should ever be able to repost anything from it, just like on Facebook. So then another interesting question comes: how such closed groups should be federated in a secure way? And I won't be surprised if it turns out that #Hubzilla / #Zap have already implemented this. Otherwise, the only option is to not federate closed groups at all if we want to keep them secure.

#Lemmy has groups support since the beginning, and they're slowly starting to federate

Does #Soapbox support groups?

the two social networks certainly do interact and can follow and respond from either one