Hi Igor,
Each shape has an interaction style associated with it which specifies the aspects of the shape for which trackers (interactive editors with handlers) are created when the shape is selected. A polygon shape is a 2D shape, which by default shows only the rotated bounds, pin and rotation trackers. To show the points use this code:
NInteractionStyle istyle = shape.InteractionStyle;
istyle.GeometryPoints = true;
shape.InteractionStyle = istyle;
Best regards,
Ivo