Luck and AC

[DM Cojo]

Can a player use luck to improve their character's AC for the purposes of making a single attack miss? Meaning, that if a character has AC14 and the creature rolls a 15...can the character expend two points of luck to temporarily make their AC 16? In game terms, this could indicate a very lucky dodge or unusually quick reaction time which caused the attack to ultimately miss. Just want to get clarification before my game on Saturday.

[Rick]

Luck points burnt typically are only added to rolls made by the character, but you can always invoke Joseph's admonition on page 314, "The judge is always right. Let the rules bend to you not the other way around".

[DM Cojo]

So perhaps the good rule of thumb here is that you can only use luck to modify your own dice rolls, unless you are a halfling? And halflings only other PC's rolls?