Alright, I rewrote some code in usercp.php so it will only update database fields for which the user specified a value. =p
I also hacked matty's script to fix some bugs, make it compatible with Opera as well as Firefox, and make it dynamically grab the security token, which shouldn't be hard-coded because it's subject to change.
http://shoutbox.menthix.net/files/invisiblemode.user.js
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