KarinsDad said:
Yes, they are.
But, the problem is that if you take the absolute micro view, then there are "workarounds".
I cannot detect his thoughts. Ok, I use Detect Magic and detect his Mind Blank spell.
Err.
I cannot scry him. Ok, I scry his famous sword.
To me, this is a waste of the protective quality of the spell.
Well, the scrying the sword trick is definitely out -- D&D consistently considers equipment to be part of the character that's equiping it, so the enchantment (excuse me, Sean Reynolds -- the spell

) covers the equipment.
As for spells, though, I'm not sure that D&D considers spells to be part of the character on whom they're cast. In some cases I can think of, they would be: an invisible, change selfed person wouldn't have a visible disguise. But in some cases they wouldn't be: a dispel magic can target an individual or a spell, even if the spell is on an individual.
I'd be surprised if mind blank doesn't cover its own tracks: that is, it makes sense for the spell itself not to be detectable. In fact, I could easily rule that the fact that Bubba is under a mind blank spell is information about Bubba that isn't detectable by detect magic.
However, true seeing, as I see it, makes the caster immune to illusions, allowing them to gain exactly the information their eyes should be gaining, no more and no less. It's not the spell that learns information about the mind-blanked invisible Bubba; it's the true seeing-caster's eyes that gains the information, now that the illusions aren't preventing the eyes from doing their work.
I'm not sure this interpretation holds up -- does it imply that invisibility is a mind-affecting power? If so, I know a game designer that'll jump all over me for suggesting that. But it may not imply that: it may simply imply that iluusions are always magical in nature and come to the eye in an inevitably magical form, and that true seeing can block these magical images while allowing nonmagical images.
Daniel