I'm learning about the Fediverse and am confused about how federation is supposed to work. I understand that there can be communities with the same name in different instances, with different content. But I also understand you can subscribe to another instance's community. For example, there are sysadmin commnunities at lemmy.world, lemmy.one, and beehaw.org (among others). If we focus on one specific community, let's say [email protected], we can find that community from any of the instances. If I go to each instance and look at [email protected] from each one, I can see the same pinned post is at the top of each one instance's view ("Calling all /r/sysadmin reddit refugees!" by DarraignTheSane).

Great!

However, if I look at that pinned thread from each of the three instances, the comment stream is different. The post itself is the same, but the comment thread is a mixed bag. Some comments seem to appear in multiple instances while others only in one or two, but never all three

lemmy.world shows 11 comments lemmy.one shows 6 comments beehaw.org shows 4 comments

On lemmy.world, the second newest comment says "Nice! It feels like home." This comment also shows up on lemmy.one however not on beehaw

The newest comment on lemmy.world says "yeeey" but doesn't appear in any other instance's view of [email protected]

This is just one specific example. Are you not supposed to get the same content, when looking at the same community, regardless of what instance you are logged into when viewing it? Or am I missing something?

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[–] [email protected] 4 points 1 year ago

There are two things in play here. One is that beehaw has lemmy.world defederated due to high moderation volume, so that connection is broken. This is part of how federation works and is to some extent inevitable. Because it's splitting community userbases, however, I do think that defederation decisions can be more fraught on lemmy than they are on Mastodon in some ways. The only solutions here are, either the moderation load is reduced to the point beehaw refederates, or moderation tools improve to make it easier for them to manage the load, or you migrate to an instance that isn't defederated.

I do think it strongly incentivizes mainstream community creators to set up shop on instances that are both large and well-moderated, to make it the most likely that the most users will be able to access that community. (Because other instances won't want to defederate.)

The other thing is that some servers that are federated still have issues with comments getting lost. This is a technical issue that is supposed to be improved with the new version of Lemmy. How I see it manifest on blahaj is that with some of the busier servers, especially lemmy.world and lemmy.ml, some comments never make it over to blahaj.

There is a workaround, sort of, which is that if I search for a specific comment by URL, that alerts blahaj to its existence, and then it appears. But I have to know the comment exists and care enough to go the trouble.