var instance = new Vintasoft.Imaging.Annotation.UI.UIElements.WebAnnotationViewerContextMenuJS(imageViewer, settings);

var value; // Type: function
value = instance.get_AddAnnotationCommentCallback();

function get_AddAnnotationCommentCallback() : Function;

A function, which will be called when "Add annotation comment..." menu is selected.
Here is function prototype "function __showAddAnnotationCommentDialog(docViewer, focusedAnnotation)", where "docViewer" parameter is an instance of WebDocumentViewerJS class, "annotation" parameter is an instance of WebAnnotationViewJS type.