I'm disappointed that I don't know, and can't find, the answer to this question: Does the Mobility feat, and similar abilities, apply when attempting an Acrobatics check to move through an opponent’s space? Thematically I'd think it would, but I cannot find it explicitly written out, which makes me question this. Is a creature generally able to threaten its own square with a non-reach melee weapon (such as a claw or longsword)?
Threatened Squares: You threaten all squares into which you can make a melee attack, even when it is not your turn. Generally, that means everything in all squares adjacent to your space (including diagonally). An enemy that takes certain actions while in a threatened square provokes an attack of opportunity from you. If you’re unarmed, you don’t normally threaten any squares and thus can’t make attacks of opportunity.
Mobility (Combat Feat) Prerequisites: Dex 13, Dodge. Benefit: You get a +4 dodge bonus to Armor Class against attacks of opportunity caused when you move out of or within a threatened area. A condition that makes you lose your Dexterity bonus to Armor Class (if any) also makes you lose dodge bonuses.