Seeing as about half of e-mail verification scripts won't accept "+" in a username, a pretty well used and specified way of using multiple addresses especially in Gmail* then I wouldn't hold out for any changes to allow for these type of rules on most sites for a good few decades.
*For non Gmail users it allows you to add any characters after your normal username in the e-mail address to add unlimited aliases which you can then individually block or filter. E.g. if your e-mail is myname@gmail.com you can (without registering it) just sign up to sites using myname+thissite@gmail.com and you will see if they sell your e-mail address on or it gets stolen and can then block that address and inform the site of your disappointment.
Biting the hand that feeds IT
