Please correct me if I am doing something wrong, and help me where I am not sure.
So, what auras could be detected on...
1) a level 3 LE human warrior (none)
2) a level 6 CE human adept (faint chaos, faint evil)
3) a level 6 LN human cleric of Asmodeus (strong law, strong evil)
4) a level 7 CG human cleric of Groetus (strong chaos, faint good)
5) a level 11 LG human paladin of Shelyn (moderate law, overwhelming good [11 HD])
6) a level 8 CE ogre (4HD) cleric of Gorum (moderate evil, strong chaos)
7) a level 6 NG tiefling rogue (faint good? strong good? Does 'aligned outsider' mean 'outsider with [aligned] subtype? Outsider with [alignment]? Both?)
8) a level 9 CE elven vampire wizard (moderate evil... faint or moderate chaos? Is the 'undead' line only for 'evilness'?)
9) a CE (fallen) Monadic Deva (14HD)? (Overwhelming good [14 HD], plus moderate chaos and moderate evil? Or Overwhelming good, chaos and evil (all at 14 HD)?)
10) a LG level 12 (ascended) Succubus (8HD) Paladin of Sarenrae (see the 3.5 succubus paladin)?
11) a level 13 CG human ghost sorceress?
Ah, detect alignment spells... What fun!
Essentially, there are two things that determine what alignment detection results you can get from a target:
1) Actual alignment..
2) Alignment subtypes due to race.
Technically, these are a function of HD, class level (for some classes) or Caster Level.
By RAW you only need to pay attention to the targets total HD/class level in aura'd classes/Caster Level, and it will ping a result from an appropriate detect spell of the appropriate strength. So, to use the funnest example you've given (10), our hypothetical Paladin succubus would detect as Overwhelming Good AND Overwhelming Evil AND Overwhelming Chaotic AND Moderate Lawful at all times.
Why would you be detecting good on evil creatures, faint where it should be strong, and so on?
Subtypes and worshipped Gods don't count for the purpose of detecting alignments, only the real alignment of the creature and its actual type or class do.
Subtypes and worshipped Gods don't count for the purpose of detecting alignments, only the real alignment of the creature and its actual type or class do.
Actually, if the creature in question is the cleric or (anti)paladin of an aligned deity, the deity's alignment is what pings stronger than the creature's. (as per 'Detect Evil' rules)
Ah, detect alignment spells... What fun!
Indeed :)
Basically, what I fail to comprehend is the 'aligned outsider' line.
Does this one only apply for subtypes, or for actual alignments, as well? If the latter is true, a good tiefling will ping stronger than a good human. Which comes across as... odd.
Same game with 'undead'. While Undead are described as inherently evil, and I guess the 'aligned Undead' line takes this one into account, one can read the table in a way that a lawful undead would ping 'lawful' in a stronger way than a lawful living creature.
Yes, it's to do with subtype:
Any effect that depends on alignment affects a creature with this subtype as if the creature has an evil alignment, no matter what its alignment actually is.
The "effect" of Detect Alignment spells is to reveal the alignment of the target creature(s). More specifically, to detect whether the creature matches the specific alignment of the spell used. In the case of the Evil subtype, Detect Evil will flag an [Evil] creature, regardless of its actual alignment.
As for undead, one can only assume that the energies that created and maintain the undead state radiate the creature's alignment more strongly than a naturally living specimen of the same alignment.