geoJSON Polygon Rings Cannot Share an Edge

source/core/2dsphere.txt

@@ -158,6 +158,15 @@ The following example stores a GeoJSON :term:`LineString`:
 ``LineStrings``. Closed ``LineStrings`` have at least four coordinate
 pairs and specify the same position as the first and last coordinates.
 
+The line that joins two points on a curved surface may or may not contain
+the same set of co-ordinates that joins those two points on a flat
+surface. The line that joins two points on a curved surface will be a
+geodesic. Carefully check points to avoid errors with shared edges, as
+well as overlaps and other types of intersections.
+
+Polygons with a Single Ring
+```````````````````````````
+
 The following example stores a GeoJSON ``Polygon`` with an exterior
 ring and no interior rings (or holes). Note the first and last
 coordinate pair with the ``[ 0 , 0 ]`` coordinate:
@@ -172,10 +181,10 @@ coordinate pair with the ``[ 0 , 0 ]`` coordinate:
        }
    }
 
-For Polygons with a single ring:
-
-- The ring cannot self-intersect.
+For Polygons with a single ring, the ring cannot self-intersect.
 
+Polygons with Multiple Rings
+````````````````````````````
 
 For Polygons with multiple rings:
 
@@ -186,7 +195,7 @@ For Polygons with multiple rings:
 - Any interior ring must be entirely contained by the outer ring.
 
 - Interior rings cannot intersect or overlap each other. Interior
-  rings can share an edge.
+  rings cannot share an edge.
 
 The following document represents a polygon with an interior ring as
 GeoJSON: