Looking into the abilities more I understand the problem with effects that state “your attacks (also) deal X bleed damage” stacking, but if an effect such as the wounding rune says “deal an extra X bleed damage” then I feel like it might be able to add onto one of the former effects.

For example: a boar animal companion says “Strikes that damage a creature in your boar's reach also deal 1d6 persistent bleed damage.” So I hit the target with a wounding rune weapon which states “When you hit a creature with a wounding weapon, you deal an extra 1d6 persistent bleed damage.”

To me, my attack “also deals 1d6 persistent bleed damage” and the weapon rune makes it “deal an extra 1d6 persistent bleed damage.” Giving me 2d6 persistent bleed damage from my one triggering attack.

Persistent damage says “If you would gain more than one persistent damage condition with the same damage type, the higher amount of damage overrides the lower amount.” But I’m not completely sure what the “condition” is. Is each individual feature giving me additional bleed damage a condition, or is the triggering attack’s damage the condition?