I want to close the loop on this issue from an administrator perspective. Some folks here helped me understand more about how this ended up in my inbox. The consensus is that this report is an individual user and probably not from an instance administrator or moderator.
A user reported some posts from a thread that they found objectionable. Then they selected a checkbox that forwarded the report to the instances of *every other user* in that thread.
https://sfba.social/@EverydayMoggie/112878587331060045