It seems to be working fine for me. Have you tried determining if there is another extension that might be conflicting? Is there any more information you can provide about what you're expecting to see, and what is actually happening?
I tested it with the following extensions running: Strain/Injury with Full Package, Message of the Day, DOE:Base, DOE:Sound, Remove Effect Tag and it appeared to be doing the right thing.
EDIT: Here's one scenario that does not seem to be working: Critical Threat, Crit Not Confirmed. No apparent mirror image processing in that case (both NPC attacking PC, and PC attacking NPC exhibited this bug).