In AD 1.9.0.11 when I have the Layer Effects fx panel open. I click on one of the field names, like Outer Shadow, , then if I press Space bar the selection check is checked and there is a halo around the check mark. Pressing space does nothing further until the name is again clicked, then the spacebar will erase the check mark. Just leaving the halo. I've never seen this action in other versions and wonder if this is as designed or a bug. Also I've never noticed the halo, what does it mean I don't see any difference.
I've also noticed that the spacebar sometimes will toggle the visibility of the selected layer. Again it only happens right after the layer has been clicked on.