Nifft said:
The difference is that true seeing penetrates invisibility (or any other Illusion effect). That's called out explicitly in the list of stuff true seeing sees through.
HiPS is not an effect of the Illusion school, is not mundane or magical darkness, etc. It's just not on the list.
Can you justify how it's identical to invisibility? Because that makes no sense to me.
Via game mechanics, HiPS is just like Invisibility except that a Hide check has to be rolled. For example, to hit that HiPS character, an attacker would have a 50% miss chance. I wasn't trying to say that it is invisibility, but for all intents and purposes, a successfully hiding character is not seen by opponents and gains many of the advantages of invisibility.
You confer on the subject the ability to see all things as they actually are.
The character using HiPS is not actually in the shadow.
The problem with HiPS is that it does not state how it works.
It does not state if shadows wrap around the target or how exactly the magic works. But, it is a Su ability for Shadowdancers, hence, it is magical.
As magic, there should be a reasonable magical counter to it.
One could possibly state that Detect Magic is a magical counter to it, but Detect Magic will only give so much info after a significant period of time.
See Invsible will not counter it.
The only core spell left is True Seeing (TMK).
True Seeing is basically designed to see through illusion and transmutation magic. HiPS is magical.
If HiPS is not illusion magic, then what kind of magic is it? It doesn't state. Since it deals with hiding and shadows, that basically shouts the Illusion school, but we are not explicitly told.
Illusion spells deceive the senses or minds of others.
Now, we do not know what school of magic HiPS is. I totally agree with you that HiPS is not explicitly on the list of True Seeing. But, HiPS Su is magical. And True Seeing states that it will not see through "simple hiding". But HiPS is not simple hiding. It is magical hiding because it is magical and it allows hiding when hiding would normally not be allowed.
I agree with you that my interpretation is not explicitly stated in the True Seeing spell or the HiPS description. But, it is a reasonable interpretation based on how other magic works in the game and the intent of the True Seeing spell.
The interpretation is "HiPS is magical hiding and True Seeing is limited to not viewing simple hiding".
And, it is reasonable that a magical special ability would have a magical counter. Especially a magical counter that costs gold to even cast versus a special ability that can be acquired as early as 6th level.
I don't think a simple Su deception ability should defeat one of the most potent divination spells in the game. JMO.
But literally, I agree that your interpretation could be viewed as literal RAW. I view this question, however, as an omission of what type of magic HiPS is, the intent of True Seeing, and a game balance issue.