Moving to: m/AskMbin!

Nah, you're good. For unknown reasons federation between kbin and lemmy.ml in particular is just fundamentally broken right now. There is some talk about this on lemmy.ml , there are a couple of threads about this topic on kbin as well somewhere, the most popular here.

Essence: Lots of speculation, nobody knows for sure, participation on lemmy.ml hosted discussions from kbin seems to be impossible right now (I tried, to no avail), federation between kbin and other lemmy instances does not seem to be impacted to the same extent, if at all?

Your understanding of how it works is mostly correct. When an instance federates a magazine, all new posts, comments, likes, downvotes, etc. will be federated/shared. But currently kbin and lemmy are not playing nice (the software that is) so it can take time or miss updates all together. Also, kbin.social is a bit jusy so there are delays as well.

lemmy.ml is blocking kbin requests, meaning kbin instances get an error when trying to retrieve new posts and comments.

It's still unclear why they are doing it, but it seems to be deliberate as they are specifically blocking the kbin user agent (some text kbin uses to identify itself to other fediverse servers).

I assume they're trying to defederate without actually limiting the freedom of their own users. By just blocking requests from kbin instances, their own users can still use kbin magazines as they please, only kbin users are excluded from federation.

I've noticed the same thing, comments are not visible. As explained below, I'm just gonna give the federation some time to do its work and then the comments will start appearing.

Two big things:

Time - Federation takes time. Especially if servers are overloaded or haven't allocated enough federation workers. Both of these things have been true at some point for most instances since the population boom.

Defederation - Different instances can defederate from other different instances. So say for example I have three instances, lemmy.one, lem.two, and kbin.three. In this example, lemmy.one has defederated from kbin.three and the post in question is on lem.two/c/community.

You now have three scenarios:

1. A user visits lem.two/c/community and sees all the content.
2. A user visits kbin.three/m/community@lem.two (or however kbin does cross instance URIs, I'm not familiar). This user sees most of the content. The limited factor here being time.
3. A user visits lemmy.one/c/community@lem.two. This user sees most of the content, but no comments from kbin.three because of defederation.

And I could be wrong, but I believe vote federation is separate from comment federation, so if that takes more time, then the comments sections might look different even if they have the exact same comments because of vote sorting.