Ha! That’s a wacky edge case. Federation is instance based though. That explanation only makes sense if no aussie.zone user subscribes to any lemmy.blahaj.zone community. Given the overlap of users (a few blahaj users are regulars on aussie.zone), I have a hard time believing that’s the case.

If the unban still hasn’t federated, try getting their mod to ban/unban again. We’ve had issues with posts in /c/Melbourne getting unpinned for other instances previously. The fix was to pin again, wait a minute or so and unpin.