I found an interesting issue, but I'm not sure if it's related to Core or an Extension. It might be related to the "Best Answer" extension.
In the source code for the HTML page, within the <script type="application/ld+json">element, for a thread with zero posts, but with a tag change, there will be an element "answerCount": 1, "suggestedAnswer": []
This is problematic because answerCount > 0 indicates to Google that a suggestedAnswer will follow. In this case, since there is no post, the backend creating this code leaves it blank with []
Learn More takes you here:
https://developers.google.com/search/docs/data-types/qapage
I believe the issue is that the "post" indicating the tag was changed is interpreted by the back end as a post or "answer" for the purposes of calculating answerCount. Maybe there is a way to ignore those "posts" that are really just Tag changes (or renaming a thread, etc.) in the code that calculates answerCount
