>I think it won't be possible since RENEWAL doesn't use a cookie like many
 >other commands that require confirmation (and are thus able to use a
 >clickable URL).

Say there was a list called L-Nittany here, then:

http://lists.psu.edu/cgi-bin/wa?LCMD1=confirm+l-nittany

Of course you need a previous LISTSERV password and most likely a cookie
in your browser, but that is pretty much a one-time effort (though
cookies do expire).

Other servers may have different file structures where WA "lives"

Pete