Alright, so I think I've found a bug.
If you run a board where you want to prevent users from changing their email, either by editing the modifypassword template or by cutting things out of the profile.php file (tried many things, like changing $show['edit_email_field'] to false whether user was on ban list or not, and commenting out whole sections). Anyhow, regardless of how I tried to work it, I couldn't remove the email input fields, because when users tried to change their passwords, they'd be redirected to error pages saying they needed to enter their email (when those spaces didn't exist).
And when I disabled Email Rules, everything worked fine.
Any ideas? Suggestion would be muchly appreciated!