Restrict "reply visibility" options

We have an internal feedback forum where we want to encourage transparency and keep all comments available to everyone in our staff. The "reply visibility" selector is causing us problems because some users are selecting "staff only" based on some random assumptions they have about how the forum should be used.

Even though the "reply visibility" selector is very useful (and we use it a lot for public forums), could you support disabling it on a per forum basis?