Jessica, it's not that onerous to put together that list of 5 or even 10 reasons for deleting posts. When you delete a post a window pops up for the mod, he checks the appropriate box, presses send and off it goes to the poster.
Not so tough, but very member friendly and could avoid a lot of messaging back and forth (making the mods even easier), as well as not upsetting someone who put though and effort into posting something of meaning to them.