Thanks Phil.

I already own BVH Helper (great tool btw.) and after your post I even checked the "More" section and found it. I really should have guessed its in that tool set).

But after running it on an animation every frame is keyframed so it seems it doesnt selectively copy/reverse only the keyframes that already existed. Unfortunately this makes further editing of the animation pretty hard.

Is there any trick I am missing or some other tool preserving non-keyframes?