I have made the patch and built a new xfce4 package that is uploaded to the testing repo.
uelsk8s: thanks for your great efforts. I upgraded to that package on my test system. It still does not solve the Quit button bug, but it does reduce the occurrence of the problem. It happens about 50% less frequently for me than it did before, but for newbies this is probably not good enough. And its not worth the effort for most to do this upgrade when they can just use the Panel Exit Button.
Anyways, thanks for trying, I might add a comment to this effect at the xfce4 bugsite so folks know that that developer's solution does not always work. Otherwise that new xfce4 package did not seem to break anything...