Having run my own test mastodon server, I can tell you that boosting is REALLY important. That's how posts propagate between servers that are not federated together.

I may get a bit technical, and it can be hard to describe but it's something like this:

Let's say that you have 2 servers, A and B that are not connected. They have their own federated timelines that is vastly different.

let's assume they have their users @a@A and @b@B that are mutuals. If user @a@A sees something interesting on theirs federated timeline and boosts it, user @b@B will see that on their own home page. But more importantly server B will now know about and download that post, and everyone else on B server will be able to see that post on their own federated timeline!

And that's why you boost, guys! It helps posts to spread.

#FediTips