Is this for purchased books or sideloaded books?
For purchased, the metadata comes from Kobo. If they have it wrong, then tell them and they should fix it.
For sideloaded books, the device reads the author from the first dc:creator tag in the OPF. This means that if there are multiple dc:creator tags with one author per tag, only the first is read. This is the way calibre, and probably most metadate updaters work . If you use calibre, you can use a metadata plugboard to set the author in a way that the device will read. This will be to set the value of the tag as "FN LN, FN2 LN2". I use:
Code:
program: raw_list('authors', ', ')