Hi again, Steve.
An interesting thing happens when I follow the steps you listed. If I place the cursor into a part of the Section Text and click Revert to Original Style from the red triangle, it successfully reverts that specific part of the Section Text back to the Novel Stylesheet formatting; however, if I highlight all of the Section Text and do the same thing (to try and revert all of the Section Text in one fell swoop) it changes all of the Section Text to a single-spaced, Helvetica font. I have no idea why it's doing that.