<Snipped quote by Dragonbud>
Well in this case, in DnD terms, it was by all technicalities Carver's turn and he chose to use charge, while charging if you enter any adjacent enemy squares then you provoke an attack of opportunity. So basically Carver was to busy with his face in the shield charging to stop and swing upwards.
In DnD terms, charging into threatened area doesn't provoke AoO.
Charging trough or out of threatened area does. So Furnace would have been able to take a AoO against Carver, but he's not hostile so the option is usually skipped. Now what the bandit did:
As a move action (at half movement speed) you can move trough threatened space. Moving trough a hostile characters space ads 5 to the roll.
If you fail you still move but provoke.
So what the bandit did was legit, he'd just have to make two tough acrobatics rolls. (one to make the jump, one against Carver's maneuver defence + 5). If he'd failed the first he'd fallen on his face, if he'd failed the second he'd gotten a stab up de hurtybits.