"You deal damage to one object held in the target’s hand or accessible on its body. The object must be something that could be drawn easily by the target as a move action (see Draw or Sheathe a Weapon on page 247). The damage is reduced by an amount equal to the object’s hardness (see Smashing an Object page 409)."
Because armor is not something that could be drawn as a move action, the sunder combat maneuver does not work on armor by RAW.
There is no general rule about energy damage dealing half damage to items, though there is the general, GM-discretion driven rule that certain attacks might be extra effective or completely useless against a given object.
GM discretion on very effective or totally ineffective attacks IS a written rule, and does apply in Society.
From CRB page 409:
Hit Points: An object’s Hit Point total depends on its item level and is modified by additional criteria. On average, a sturdy piece of equipment (such as a weapon or a suit of armor) has a number of Hit Points equal to 15 + 3 × its item level. Any other piece of equipment has a number of Hit Points equal to 5 + its item level. Any item of level 15th or higher receives an extra 30 Hit Points. Very large objects may have separate Hit Point totals for different sections. Objects do not have Stamina Points.
Damaged Objects: A damaged object remains functional (though it has the broken condition; see page 273) until the item’s Hit Points are reduced to 0, at which point it is destroyed. Damaged (but not destroyed) objects can be repaired with the Engineering skill or a number of spells.
Ineffective Weapons: Certain weapons can’t effectively deal damage to certain objects. Most low-level melee weapons have little effect on metal walls and doors. Certain pieces of equipment are designed to cut through metal, however.
Immunities: Objects are immune to nonlethal damage and to critical hits.
Vulnerability to Certain Attacks: Certain attacks are especially strong against some objects. In such cases, attacks deal double their normal damage and might ignore the object’s hardness.