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Bleeding Critical (Combat, Critical)
Your critical hits cause opponents to bleed profusely.Prerequisites: Critical Focus, base attack bonus +11.
Benefit: Whenever you score a critical hit with a slashing or piercing weapon, your opponent takes 2d6 points of bleed damage (see Conditions) each round on his turn, in addition to the damage dealt by the critical hit. Bleed damage can be stopped by a DC 15 Heal skill check or through any magical healing. The effects of this feat stack.
appears to be in contradiction to
Bleed: A creature that is taking bleed damage takes the listed amount of damage at the beginning of its turn. Bleeding can be stopped by a DC 15 Heal check or through the application of any spell that cures hit point damage (even if the bleed is ability damage). Some bleed effects cause ability damage or even ability drain. Bleed effects do not stack with each other unless they deal different kinds of damage. When two or more bleed effects deal the same kind of damage, take the worse effect. In this case, ability drain is worse than ability damage.
So, do multiple Bleeding Critical hits ramp up the bleed damage, to multiples of 2d6?
Do I roll 2d6 several times, taking the highest result?Is the 'effects of this feat stack' meaning something different altogether?
The bleed rule saying bleed does not stack is a general rule. The feat is a specific rule.
Specific rules always trump general rules.
As an example if you crit twice the victim takes 4d6 points of bleed damage.