Just because I can't think of a reason to connect displacement to reflection doesn't mean there isn't a time when someone would want that.  I have to wonder why someone would do that...  As in what would they likely be trying to do?

I really don't know what the problem here is.  Yes, the material room can be confusing, and there are only a few here who truly seem to grok it.  But I don't think dumbing it down is the answer.

What I'd like to see would be for SM to separate out all of the legacy content into degrees of usefulness.  For example all of the P4 lights really should be removed or put someplace where it is explicitly clear that they are for the P4 renderer and older content.  The figures should be kept, but why can't they be minimally updated.  Not brought up to modern standards necessarily but just given the 15minutes of attention an experience user would give them.  Run EZSkin on Posette and Dork, clean the models of .bum files and their references... 

Give new users a basic set of materials, or better yet EZMat, and they'd have less reason to visit to the mat room in the first place.

Also, I have to chuckle at "telling Poser what Galaxy you are in" when using multiple infinite lights...  My current scene has three infinite lights (mostly for diffuse).  I'm rendering items for use in a 2D game, and that was the combination that gave the desired result.  There's probably not a thing that can be done that is "wrong" 100% of the time.  Even in moderately realistic scenes I still sometimes point an infinite light upward (in tandem with the down-pointing "sun") to simulate IDL.