I have an object whose script does things when an avater enters an area. It does this using llVolumeDetect. The problem is that users can't click on things behind the "invisible" trigger area, they instead get the trigger area itself. (It has a 0 alpha texture)
I have been told that the llVolumeDetect function and the events collision_start, collision_end, are much faster than code that uses SensorRepeat and sensor which is why I need a trigger area in the first place.
What's needed I think is some kind of flag for objects or parts of a linked object that makes it impossible to click on that part without being in the editing mode. Of course they'd have to be manipulatable somehow, possibly by using the highlight alpha option, or just doing ctrl-3. The thing is, there's currently no way to make a truly invisible object for use as a script trigger, an object that is really "transparent" to the user.