Currently, there is no way of knowing WHO accepts a file into WPA. This is especially important with files being loaded in bulk (via GDX or folder). I use a default id of ADMIN for these files and that id stays with the file all the way into the system. Even though we require a user to manually review and accept the file into the system. There is no history of who that user was. No accountability for a bad file accepted into the system.
The accepting user's id should be displayed in the UI on the compliance tab as well as under the material declaration tab for each version.