The GPL *does* place a burden on a third party who wants to use that
    code without the GPL, because that third party must obtain it from a
    place other than the collective (GPLed) work containing it.

This is another example of a misconception about the GPL.

If the person who writes the addition cares about the matter, he can
attach his own copying permissions to the addition.  Then, if you
wish, you can get a copy of the combined work, delete all but the
addition, and use that under the terms its author set.

If the author of the addition did not state copying permissions other
than the GPL, then if you wish to use his work on other terms, legally
you would need to contact him to get permission.  But that isn't
because of the GPL.  That is generally true.

    It also creates a problem for the original author...

I couldn't understand this, so I have no opinion about it.

    I somehow doubt that anyone on this list cares about some hypothetical
    person you claim to have once talked to.

I think the other people on this list are capable of making up their
own minds as to what they care about.

If they are sincerely interested, and it proves relevant, I could even
search for old messages that would contain the email address of the
person I spoke about.  The conversation happened a couple of years
ago, so searching would take some effort.

Meanwhile, one of the principles of civil discourse is that you
shouldn't make accusations without having grounds for them.  Here you
have accused me of passing fiction as fact, with no basis except that
you think it might be difficult for me to prove you are wrong.