Okay, I'm not convinced the "one DP per action" argument holds water here. You're not upgrading or downgrading the same skill check twice or trying to activate stuff like Anatomy Lessons twice for the same attack action.
Let's say a Rival maneuvers to engage, you PEA, he maneuvers to engage again, suffering 2 damage.
You have two completely separate instances of a trigger that you can react to, and neither trigger is an action . Either you cannot spend Destiny points at all because "not an action" (doesn't make sense at all) or this talent works by a different rule, allowing it to spend exactly "one DP per maneuver" (kind of makes sense.)
That's the way I'm going to playtest it, and unless they include language like "this talent can only be used once per round/opponent/whatever", I'm going to assume that the limits of the Destiny Pool are all the limits I need.
Edited by GranSolo