Statement:

"Interior rings can share an edge."

Page: http://docs.mongodb.org/manual/core/2dsphere/#geojson-polygon

I have tested this, and spoken with Greg Studer, and this functionality, while desirable, has not been implemented.

Be very careful when investigating this, by the way.

You may think that the polygons defined by the points

[ 0 , 0 ] , [ 1 , 0 ] , [ 0.9 , 1 ] , [ 0.1 , 1 ] , [ 0 , 0 ]

and

[ 0 , 1 ] , [ 1 , 1 ] , [ 1 , 2 ] , [ 0 , 2 ] , [ 0 , 1 ]

share an edge between the points [ 0.1 , 1 ] and [ 0.9 , 1 ] .

In fact, they do not.