<Reply-all> may not be the problem
During the last international mail-storm here , I watched hundreds of "unsubscribe" emails being sent to the entire list. My first thought was that many colleagues were foolishly hitting Reply-all. In fact, they were actually (still foolishly) using Reply.
Most list-servers in my humble experience simply treat a Reply as a Reply-to-list; you need to use a different admin address if you want out. List members tend to forget or lose this vital piece of info. At work, entire departments may get signed up to new lists, with little warning.
Some list-servers at least may trap any unsub requests, but it doesn't seem to be default.
Still, that's my observation as a user, not an IT admin of any sort.