FBX support

Removing it, and the file does not import.

Try remove this also

         LayerElement:  {
            Type: "LayerElementSmoothing"
            TypedIndex: 0
         }

Works.  What is your train of thought? 

What we have been dealing with is the file you exported from Maya without going through Nvil.

Now here is the file which I imported from your Maya file into Nvil then exported to fbx.
http://www.digitalfossils.com/Download/FBXCreaseTest_Nvil.rar

Geo imports correctly, but without crease data. 

 I had a look  at it in notepad and it is without formatting so hard to read.

Can you read any thing in it?

Yeah, just doesnt have any word wrap, so is basically a single line of code.  Ahh....I can read in sublime text.

It opens in my NotePad fine.

No. It is not NotePad. Use WordPad.

I found what is missing:

Seems you need this header:

; Object properties
;------------------------------------------------------------------

Objects:  {
   Geometry: 140747960, "Geometry::pCube1", "Mesh" {
      Smoothness: 3
      PreviewDivisionLevels: 2
      RenderDivisionLevels: 2
      DisplaySubdivisions: 0
      BoundaryRule: 1
      PreserveBorders: 0
      PreserveHardEdges: 0
      PropagateEdgeHardness: 0
      Vertices: *24 {

These are the smooth preview settings that are needed for Creases.

Adding that to creasedCube7500_A.fbx, and it imports into Maya correctly.

I suspect these settings too. Why Maya needs them? Do I need to set all of them?

They are the smooth preview settings.  To export creases,  this preview mode has to be active (subdvisions).  I will delete each setting to see when it breaks.

FYI,  all of those settings are features Nvil already uses.

Yeah, they are needed in order to support default functionality in Maya.

Somebody would have to test with Modo/Blender to verify those apps.  They may not even support Creases in FBX regardless.

If it works correctly for Maya, it will work in Mudbox/3dsMax most likely.

Try this
http://www.digitalfossils.com/Download/NVil-Apr-19-17.rar