I was just about to lose it while reading a thread about sources of damage stacking/not stacking due to them both being "equal to X fraction of your level" and some people claiming "your level" is the source so they don't stack.
It all goes back to a wonderful Paizo decision via FAQrrata.
This means that if you were say a fighter who got your con mod to damage via a class feature named "unending bullshit feature" and took a feat that gave you 1/2 your con mod to damage that they would not stack as the feat and the class feature are not the source but the attribute is...Paizo wrote:Do ability modifiers from the same ability stack? For instance, can you add the same ability bonus on the same roll twice using two different effects that each add that same ability modifier?
No. An ability bonus, such as "Strength bonus", is considered to be the same source for the purpose of bonuses from the same source not stacking. However, you can still add, for instance “a deflection bonus equal to your Charisma modifier” and your Charisma modifier. For this purpose, however, the paladin's untyped "bonus equal to her Charisma bonus (if any) on all saving throws" from divine grace is considered to be the same as "Charisma bonus (if any)", and the same would be true for any other untyped "bonus equal to her [ability score] bonus" constructions.
This is nowhere in the books and causes so many problems that they had to state over and over this is only true for ability scores as they are special bunnies and other things may or may not have such nested sources, but don't use this FAQ to draw conclusions.
*ARGGHHH*
/rantoff
Sorry just got reminded of that and it made me furious.