First off, let me say that this plugin is doing exactly what I want, restricting each user into posting only in their own specific category. So this plugin has solved 90% of my challenge. Unfortunately it only seems to set the author category when using 'Posts > Add New' or through the dashboard QuickPress palette.
It does not seem to work, however, when users make a post using a front-end editor (http://wordpress.org/extend/plugins/front-end-editor/). New posts made from the front-end default to 'uncategorized,' regardless of the user; the 'author category' is ignored and not set.
The Front End Editor post creation method is fairly simple (see https://github.com/scribu/wp-front-end-editor/wiki/Creating-posts), and I'm hoping it's possible to tweak this code to pull and set the author category.
Any help would be appreciated.
I have no link to preview, development is still local only. But this is a generalized enough question that an example isn't needed.