Read the feat. If it lists the effect as mind-affecting, then that's what it is, if it doesn't, then it isn't.

Not entirely true. Suggestion and Charm Person almost literally say that people would still not do anything that common sense would prohibit.

That's because the spells your citing are on the low end of mind affecting. Also, someone guarding a cell affected by Charm Person may still let someone out of a jail cell - You know, the whole best friend all my life vibe.

Non-Mind Affecting things are not irrational. Also, I'd imagine the terrasque has one heck of a circumstantial bonus on intimidate checks.

Sorry, I forgot to include the requisite 'unless explicitly stated otherwise'. I guess I just assumed that it was understood, given the system we're discussing.

...Isn't there a spell called suffocate? If it can't replace damage done by Suffocation...wouldn't that spell work perfectly?

Well, maybe the designers were on different pages about intelligent undead. I mentioned the tarrasque ability because the Allip description mentions them being targets of mind control and their ability damage defense. It seemed odd they would mention it at all if they were immune in the first place.

There are specific spells that mimic the effects of mind control but are capable of affecting undead. See 'Control Undead' for the most common form.

There are many magical items specifically made for dragons in the supplementary books, so I think your assumption that they aren't portrayed as using magical items is demonstrably false.

Here is what the rules have to say about size and magic items:

'When an article of magic clothing or jewelry is discovered, most of the time size shouldn’t be an issue. Many magic garments are made to be easily adjustable, or they adjust themselves magically to the wearer. Size should not keep characters of various kinds from using magic items.'

Thus dragons are capable of using vast numbers of magic items even from the core rulebooks, including (but not limited to) rings, amulets, belts (as weird as that sounds), and virtually anything else that is intended to be worn or carried on their person. They might have little use for weapons or armour, but stat boosting items, wands, and virtually anything else are accessible to them.

The idea of a dragon holding a staff in one of its talons might seem odd, but consider the alternative: a dragon with a genius intellect, talons that function as well as hands, and deep magical understanding refusing to use a beneficial magical item because it's too small? Preposterous!

Perhaps, but it doesn't change the fact that I haven't seen them portrayed wielding magic items.

I see them wearing "jewelry" all the time, which in D&D could mean plenty of magic items.

Control Undead/Command Undead are spells that aren't mind-affecting, but they do establish some control over undead.