The emails are stored in $DataDir/emails. You can add yourself to that list by setting an email address in your preferences.
The mail is sent using the SendEmail function.
Since you set and unset your email address using your preferences, this removing yourself from that list is tricky if you surf the net from lots of places and use lots of browsers. Assume you used to surf from A. You used A to set your email address. You then switch to B and decide not to add your email address. You will still get notified of changes! Now, if you don't have access to A anymore, it might seem that unsubscribing is impossible. Not so.
You just have to subscribe again and unsubscribe. UpdateEmailList takes care of that.
Note: With all due respect, this function is quite lame. You need to check the box all the time if you want to be notified and only works for your own editing, nothing more. Also, all 'subscribers' are listed on the To: field, bad, bad thing... This should be completely removed on the 1.0 release.
I have created an external script that monitors a UseMod wiki and periodically emails about updated pages. It does all the bad things about allowing everyone to see the "to" list and being emailing everyone about every change, but it farms email addresses out of a wiki page and is thus basically zero administration. It works for us and it doesn't require admin access to the wiki. See ExternalPageMonitorScript for the script. (DeweySasser)