[Milhouse]

Those are basically some of the backup files that were used to recreate the library on the MySQL server. They are no longer needed since the library has since been reimported, but they're handy as a backup incase something ever goes wrong.

Surely the .actors folders contain all the cast artwork, references to which have now been imported into MySQL, and if you delete those .actor folders (and the artwork they contain), none of your other clients will be able to find and display the cast artwork (as the shared database will now be referencing non-existant files).

So if you want to view actor artwork in the GUI on all of your clients, you really need to keep those .actors folders, but if not, then delete them.

Personally I would prefer a single, shared, .actors folder for all my movies (located in the root of each source). The level of cast artwork redundancy is quite horrific with the current approach.