GTK+ can focus a paned widget (the paned itself, not one of its children) to allow moving the handle by keynav. The builtin style renders the handle with the selected color to make this obvious. Of the installed themes, only Mist seems to share this nice a11y feature with the builtin theme.
It would be nice if nodoka could do the same.
To try this yourself, open gedit, activate the sidebar, move the focus in the document, then hit f8 twice. now you should be able to move the handle between the sidebar and the document with the arrow keys. If you do this with the Mist theme, the blue color will make it obvious where the focus is. If you do it with Nodoka (or any other installed theme), it is a guessing game.
Looking at the code, it should be enough to pay attention to the selected state when drawing a "paned" handle.
Created attachment 327967 [details]
Proposed Solution 1
I've put together the simplest way to implement this in nodoka. We need to test whether there are any regressions before adding it to stable releases of fedora. I'm building a package with the fix (and fix for Bug #477941) for rawhide though.
The said package has just finished building:
Works great, thanks.
gtk-nodoka-engine-0.7.2-5.fc10 has been submitted as an update for Fedora 10.
gtk-nodoka-engine-0.7.2-5.fc10 has been pushed to the Fedora 10 stable repository. If problems still persist, please make note of it in this bug report.