If I'm reading you right, then that means I'm not the only person who interpreted "delete" to mean that I'd be removing the notification and the original if I deleted. It took a long time (several years, in fact), before I finally questioned that assumption and cleaned out my inbox! ...so yeah, I do think there needs to be some kind of a more intuitive explanation, additional text on the button, or something.

It doesn't hurt those folks who already know how it works, and it's helpful to those who don't and/or are a little uncertain.