Case sensitivity and equal values for e-mail fields

I never noticed this before but a client put my attention to it. When e-mail fields are being checked for equal values the case of the characters is also being put to the test, which may be a bit overkill.

I understand e-mail fields are just one way of applying the equal values-check, and there are definitely circumstances which demand a case sensitive input field.

So my question is: is there a way to work around this, be it in the UI (an extra checkbox which asks if the case should be checked as well - this would make this topic a feature request), be it by adding one or more lines of code in my template.php?