a small difference, but important to how people use the site
Someone just needs to follow. The community owner either needs to seed the community to big instances using accounts on them, or people who find the community via other instances need to subscribe and know that fresh content will come. Then they can boost older content from the hosting site.
Things take some conscious effort here. That isn’t necessarily a bad thing.
“Then they can boost older content from the hosting site.” No that’s the problem. Like you yourself said back catalogues arent fetched. They can’t see the older content to be able to boost it, they’ll only see new content.
If my instance follows a community at time t = T, and your instance starts following it at time t = T+10, I can boost content posted between T and T+9 so that you can see it.
Meanwhile, if people on the hosting instance boost things posted from times earlier than T, we both get to see them. Then, once they’re visible to us, we can continue to boost them for new instances to see.
If boosting is meant to be a solution to the back catalogue problem, then it’s a horrible way to do it. You’d have to go through and boost every single post from before the hosting instance was followed, and then it’d only show up the user page of the guy who went to all of that effort? (or, realistically, bot).
If what I’m saying is accurate (and I’m still not sure because this is admittedly a bit too complicated for me) then it doesn’t sound very useful since individual profiles aren’t nearly as important in a forum context when compared to something like twitter, and especially when you can just upvote something and have that show on your profile. Unless I’m mistaken and anything you’ve upvoted doesn’t propagate to another automatically instance while boosts do… but I don’t think that’s a big enough distinction to have two different buttons? You could just have an upvote also do that.