A big shoutout to @Wilhelm Fitzpatrick for this info: basically, both on the federation (diaspora) and fediverse (mastodon), if a post is created, it's broadcast to everyone who follows the creator of the post, and thus it appears on the hubs/servers the followers are on.
So let's say I create a post here with my friendica account. Both @Rafu ?? :heart_pan: (on tabletop.social, a mastodon hub) and @Wilhelm Fitzpatrick (on joindiaspora.com, a disapora hub) follow me. This means that my post is now visible on both their hubs. Specifically, if I add a hashtag to my post, that hashtag is now on their two hubs, and can be searched/filtered for. And if they post (or reshare) the hashtag, it will spread over to all hubs of their followers, and so on. It's not retroactive, i.e. my post won't show up on their follower's hubs, but those followers could decide to follow me and if I made another post (or re-shared my own post some time later), it will show up (and be discoverable) on their hubs too.
This actually sounds more complicated than it is. Basically, while it's not perfect, hashtags do propagate through the fediverse and federation.
- make a public post with the #gplusRPG hashtag
- follow the hashtag itself so that other people's posts show up in your stream
- follow new people
- from time to time make the public post again, so that it reaches farther and farther :D
A big thanks also to whoever added the #gplusRPG hashtag to the #3x3RPGs posts (I think it was @Michael Miller?). The hashtag has piggy-backed the post's success, and I find the idea very good because #3x3RPGs is a beautiful way to introduce yourself to other RPG players. Good job!
Michael also posted the hashtag over to twitter, thanks for that too! :D