When a section is disabled by setting the Visible property to false, the section remains visible in the designer without any visual indication that it is invisible when rendered. Adding such a visual indication would allow users to more easily see that it is disabled.
Having a cross over the section, making it disappear from the designer window, or showing somehow it is disabled would make it easier to understand, as currently the only way to check this is by reading the value of the Visible property in the Properties pane