Currently, Herald rules that culminate in "Send me an email" respect user notification preferences. This may degrade the email to a notification or drop it entirely.
Herald rules should be stronger than notification preferences, and we should specifically override preference-based behaviors when a recipient comes from a Herald action.
We may also want to add a "Send me a notification" action, which works like email but forces the event to degrade to a notification if there are no other circumstances which would cause email delivery. In particular, it's possible that some users currently rely on the "Send me an email" behavior plus preferences to receive notifications, although it seems somewhat more likely that this is just fairly rare in the wild.
(The "Add me as a subscriber" action shouldn't punch through preferences, and should just work like you were normally CC'd and respect preferences.)