Important to note that’s not necessarily Kbin. Some of the major instances of Lemmy had an issue where they were blocking inbound Kbin traffic but allowing their traffic out.
It was unclear if it was somehow intentional or the result of a bug in their most recent upgrade.
Just a note,
It was shown a lot of the recent threadiverse federation issues were/are being caused by Lemmy. Major Lemmy instances were/are intentionally or unintentionally (due to a bug in their platform), blocking inbound federation traffic from Kbin and Lotide. While allowing their own outbound to go through.
The jury is still out on if it was an oversight/issue with their latest release, or something more nefarious on the part of the devs with regards to competition.