Question

Can I have multiple feedback panels and determine somehow which one belongs to what?

When I tried to add more than one, all validation messages go to all panels.

Answer 1

You could use an IFeedbackMessageFilter as you found out by yourself. As for the negated filter mentioned in your answer, I suppose you want to catch any previously undisplayed message in a final FeedbackPanel. This can be archived using a FeedbackMassagefilter with the following accept method:

public boolean accept(FeedbackMessage message) {
    return !message.isRendered();
}