Your steps match mine. However, I'm not getting an "Action With No Effect" prompt; instead, the server acts like it's processing, and redisplays the page, but doesn't actually make any changes.

That fixed it. Thanks!

I don't see any error trace in my web server logs (/var/log/apache2/error.log, /var/log/apache2/other_vhosts_access.log). I may have been unclear in my description: the error message appears at the top of the Diffusion commit page, but the page appears to work fine otherwise. It seems as if Diffusion is generating an error and catching and showing it but is otherwise working fine.

1.8.8 (as shipped with Ubuntu 14.04, in case that's relevant).

Accepting an audit seems like the common or expected action of everyone using Audit, and therefore worth streamlining (similar to how Ctrl-Enter streamlines posting a comment), rather than being one particular developer workflow.