A Character with the Power Attack feat can decide to use a quarterstaff as a two-handed weapon and apply 1.5 × Strength bonus to the damage roll, plus double the number he decided to subtract from the attack roll.
Now a Monk that decides to use Flurry of Blows with the same weapon must follow the ruling in the Player's Handbook (41):
When using weapons as part of a flurry of blows, a monk applies her Strength bonus (not Str bonus × 1-1/2 or × 1/2) to her damage rolls for all successful attacks, whether she wields a weapon in one or both hands. [...]
In the case of the quarterstaff, each end counts as a separate weapon for the purpose of using the flurry of blows ability. Even though the quarterstaff requires two hands to use, a monk may still intersperse unarmed strikes with quarterstaff strikes, assuming that she has enough attacks in her flurry of blows routine to do so.
The quarterstaff, despite being a two-handed weapon, is treated as two separate weapons in this context but it still requires both hands to be used.
That wouldn't be much of a concern per se, but what if the Monk decides to use the feat Power Attack with the above class feature? How should the quarterstaff be treated in this case?
- As a Two-Handed weapon. Power Attack doubles its bonus.
- As a Double weapon. The Power Attack bonus is not applied to the light end of the weapon.
- As two One-Handed weapons (e.g. two clubs). Power Attack affects both ends but its bonus is not doubled.
Or how is it generally ruled?