Steps to reproduce
Log in as testy
Post a work with a co-creator newer than testy, whose name is far enough from "testy" in the alphabetical order (e.g. "bluewinterday")
Go to testy's work listing (or any listing where the new work can be seen)
Sort by: Author, then "Sort and Filter"
The work will be listed around T (for testy).
What should happen
The work should be listed around B (for bluewinterday), since the work's byline reads "bluewinterday, testy".
Byline sorts the authors. The field authors_to_sort_on does not sort the authors, so we seemingly get them ordered by primary key.