When someone posts something on a server he joined, the post doesn’t appear directly on the community from another instance. Why is that?

  • I think you used the correct word: fetching. The other instance has to go through everything new coming from the first instance and sync itself up. That takes time. How long? Depends on the machine and the load.

    Also, if the comment does not appear at all the two instances might not be federated. That’s a whole different issue.