Thanks for the suggestion!
Our plan right now is for submitted questions to be visible initially only to the panel creator, who can then approve or dismiss them. Once approved, a question will be visible to other panelists, and once at least one panelist has answered the question, it will become visible to the world.
The reason for this is that when questions are public, the questions themselves can be avenues for abuse, harassment, or sometimes they can be repetitive or self-aggrandizing ("less of a question, more of a statement", etc.).
Panels can attract a large audience. Since the point of panels is to allow panelists to post while others read in order to keep the signal to noise ratio high, we want to make sure that questions don't become an avenue for noise.