On March 1, 2018, the @conversation group mention and the drawing tool will no longer be accessible in InVision comments. Please see our announcement for complete details.
You can add a sketch/drawing to a comment by clicking on a screen to add a comment, then clicking the pen icon. A new screen will pop up that allows you to draw on the screen, add text or shapes, and customize colors. When you’re finished with your drawing, click I’m Done.