And my point is that Pluviouville is reporting that it is not possible. I am accepting this as an accurate report of the user's experience in that document. Paul pointed out earlier that this may be due to document corruption.

Further, if you are attempting to create a new style and your cursor is in text formatted with a style already nested ten-deep, you will not be able to create a new style in Word 2007-2013. You could in Word 2003; the modify style dialog would be launched with no style being shown as the based-on style. That does not happen in the ribbon versions.