Telling Blow, Death's Ruin, and critting undead

[John Campbell]

i would not allow the sneak attack dice.
simply because if you did then a keen scimitar would be good against undead, despite the fact that a keen weapon is no better than a non-keen weapon against crit immune enemies.

A keen flaming burst scimitar is better against crit-immune enemies than a non-keen flaming burst scimitar, according to the rule I quoted above. The inability to do critical damage to certain enemies is not a moral commandment saying that no effect related to critical ranges can ever give you any benefit against them.

And burst damage vs. crit-immunes is the nearest equivalent I can come up with that's clearly and explicitly covered by the rules. The rule that covers it only talks about weapon qualities and specific weapons, though. Is "weapon quality" here a technical term that means "special ability"? It doesn't seem to be used as such anywhere else. Does "does SA damage on a crit" become a quality of any weapon my Rogue picks up? Or does the quality have to be innate to the weapon? I dunno.