Full disclosure, this diagram is not complete. For example:
- If someone followed by someone on your instance replies to a public toot, that public toot will end up in your federated timeline.
- If someone on your instance follows someone who boosted Foo's public toot, Foo's public toot will end up in your federated timeline.
... but I didn't want to make the diagram too 🙃 , you know?
It also explains why smaller instances have quieter federated timelines.
People on smaller instances really benefit from the people they follow boosting good posts. It gets new people into their federated timeline, giving them more interesting folks to follow, which gets more people into the federated timeline... and so on!