Go to the bugzilla query form. Click on a component. Now hit "Page Down" as if you are looking for another component to add to the one you clicked. The one you clicked is deselected and the one at the bottom of the currently displayed portion of the list is selected instead. Compare this to using the scrollbar to move down after the first click. In this case, the one you clicked remains selected, so you can use ctrl-click to add a second selected item. This is correct behavior.
I don't think so.
I don't understand why you changed the component to "mouseconfig". This has nothing to do with mouseconfig. I also don't understand your assertion that the current behavior is correct. It differs from every other browser I've worked with, including netscape 4. It seems obvious to me that if I can select multiple items using the scrollbar, I should also be able to select multiple items using PgUp/PgDown. Please clarify your position.
The mouseconfig change was unintentional. It was from testing. I was saying that I probably wouldn't change this at this point. If it gets fixed upstream, I'll pull it in.