[RobAley]

One less technical way I've seen this handled is with a footer something like:

  ----
  If your friend or colleague has forwarded this to you
  and you would like to SUBSCRIBE to our mailing list,
  click here.

  If you are the subscriber ([e-mail]) and 
  would like to unsubscribe, click here.
  ----

The unsubscribe page also has large text with the e-mail address that has been unsubscribed and an undo button, and the unsubscribed account is sent one more e-mail (after a short period) confirming the unsubscription with a link to re-subscribe if they want to.

It doesn't prevent malicious unsubscription, but help to prevent or reverse accidental unsubscriptions of the type in the article. It also "works" in all email clients.

[pc86]

Unfortunately that doesn't do anybody any good when you Ctrl+F "unsub" and click that link.

[RobAley]

The e-mail address and undo button on the unsubscribe web page would help. Or maybe add a title, something like:

  ----
  HOW TO SUBSCRIBE OR UNSUBSCRIBE
  ----

  If your friend or colleague has forwarded this to you
  and you would like to SUBSCRIBE to our mailing list,
  click here.

  If you are the subscriber and would like to 
  unsubscribe [e-mail], click here.
  ----