With spear dancing I can use Shelyn's holy Weapon the glaive as a double weapon for TWF. other deities have daggers and the like which are usable in TWF.
I'd assume that symbolic weapon gives bonuses to both ends of a corresponding double weapon or both daggers.
What are your thoughts?
Symbolic Weapon (Su): When wielding his deity’s favored weapon, the sentinel gains a +1 sacred or profane bonus on attack and damage rolls. These bonuses increase by 1 for every 3 levels he has in the sentinel prestige class (maximum +4). His deity’s favored weapon also functions as a holy (or unholy) symbol when wielded by a sentinel.
Other abilities like the paladin's divine bond or the corresponding warpriest ability explicitly call out giving the bonuses to only one end of the weapon.