When you are admin and set the option "Do you want to be notified when a user uses the Notify Post option? Normally these are just sent to Moderators." you get double notifies if you are also set as moderator for a certain forum.

Not unlikely to set yourself as moderator for visibibility reasons.

my fix?

change
Code
	        $notify_array[] = $admin;;

into:

Code
	        if (!in_array($admin,$notify_array)) { $notify_array[] = $admin; };

You can also save a bit of duplicate code in there for the e-mailing by checking for an empty array, and if so, add the main admin id to the array.

[Linked Image from siemons.org]