Marc,
The idea of a closed list is just that.  The list owner does not have to
add you just because you ask.  If you were to forward a request from
someone else, that does not mean that the owner will add them.  The
correct procedure for changing any information on a closed list is to
send mail to the list owner directly.  The owner can then make any
necessary changes he feels are necessary.  The owner could delete you
as one ID and add you as another easily.
 
As to why a list is closed, that is up to the list owner.  It's his list
and he can have it his way (just like at Burger King).
 
For the number of times that the changing of USERID and NODE for a user
are necessary, I think that ADD with the new name@node and then delete
of the old name@node should be sufficient.  As far as just changing your
name without changing your address, ADD will just update your record.
(If the list is subscribe=open and verify=store).