Communities on other instances, for example lemmy.ml, are unaffected by this. Lemmy.world and beehaw.org users will still be able to interact with those communities, but posts/comments from lemmy.world users won’t be visible to beehaw.org users, as defederation prevents our posts/comments from being sent to the version of these posts hosted on beehaw.org.
Still, having this documented somewhere would be nice.
Anyway, it would mean that there is not much reason for A to also defederate from B, if T (you probably guessed it) was Threads. Though Users from B could still be quoting Users from T and/or be influenced by Users from T, but the impact from T on A appears to be very minimal in the given scenario.
This matches what was said on/about
lemmy.worldwhen they were defederated frombeehaw.org. https://lemmy.world/post/149743:Still, having this documented somewhere would be nice.
Anyway, it would mean that there is not much reason for A to also defederate from B, if T (you probably guessed it) was Threads. Though Users from B could still be quoting Users from T and/or be influenced by Users from T, but the impact from T on A appears to be very minimal in the given scenario.