OK, so Angelskin armor or material worn hides evil auras by cloaking it with a good aura. But, does the aura detect as magic or what is necessary to recognize the supernatural blocking of this effect?
So, if I cast Detect Evil and the NPC wearing this is a 10HD evil cleric this material shows he is a neutral NPC. I cast detect good and I can see the detect good of the item? What spell can tell me if there is something blocking?
Note that the cleric needs to display their unholy symbol to cast a lot of spells, which would be a pretty obvious hint to their affiliations (Of course, it might be too late by then)