You are looking at the wrong thing. Kobo does not use the file name unless the book has no internal metadata. It does use the file name for formats such as TXT, CBR and CBZ. But for ePub, it uses the internal metadata.
Calibre will updated the metadata when sending the book to the device. You either have the author as "Blish, James" in calibre, or are using a metadata plugin to set the author to the author_sort when sending the book to the device.
If it is a metadata plugin, I recommend removing it. Or changing it to:
Code:
program: raw_list('authors', ', ')
That will populate the author when sending the book to the device in the format that Kobo likes.
If you are putting the author names into calibre as "LN, FN", then you will need to fix this before you will be able to get them onto a Kobo device properly. In general, it is better to have the author as how it is written and use the author_sort for "LN, FN". If you prefer that version displayed in the calibre library you can. You can use the Quality Check plugin to search for a fix authors with commas in the name.