I was trying to set up help desk software, and couldn't find anything that worked properly, so I've hacked a Q2A plugin to allow for asking questions only visible by experts, or whoever you choose. Still needs some work, I'd like to allow anonymous posting of such questions (while not allowing ordinary anonymous questions), but soon enough.
Help debugging would be nice, if anyone is interested in it. Basically how it works is, when asking a question, one can choose whether to ask publically, or privately. Private questions are hidden, but the hidden tags are taken off, so they look normal, but only show up on the "expert questions" tab, and only users marked as experts (not necessarily the same as Q2A EXPERT level...) can comment or answer, along with the OP'er.
Lots of potential, hopefully this will be useful for allowing confidential question submission. It may still be rough around the edges, though. Here's the code:
and here's a screenshot of the admin, fwiw:
And here's one of the options on the ask form:
And finally, one showing number of open (w/out selected answer) private questions on the nav tabs: