I am slightly closer to identifying the problem. "Edwin A. Abbott Zeta" yields the following content.opf entry on the Kobo:
Code:
<dc:creator opf:role="aut" opf:file-as="Abbott Zeta, Edwin A.">Edwin A. Abbott</dc:creator>
<dc:creator opf:role="aut">nbsp;Zeta</dc:creator>
This results in the book displaying and sorting with the author "Edwin A. Abbott." Changing the content.opf as follows yields "Edwin A. Abbott Zeta," sorted as "Abbott_Zeta"—the desired result.
Code:
<dc:creator opf:role="aut" opf:file-as="Abbott Zeta, Edwin A.">Edwin A. Abbott Zeta</dc:creator>
Now the only question is how to accomplish this automatically.