Red lines appear at surface edge when control points are selected?

Red lines projecting from the edge of a surface now appear when control points along the edge are selected. I assume these lines are intended as guides for moving control points.

How do I control whether the lines are visible?

Is this a new feature or a feature I have not encountered before?

Hi David - the indicators, red and green, show the + U and + V directions. These have been there since V5. The colors floow the CPlane X and Y colors. They are some proportion of the control polygon length so are more evitent on sparse surfaces. As far as I know there is no control for these.