You're right Bill. (At least insofar as LO 4.2 is concerned.) Though it
works for AOO so seems this is a place where the two have diverged.
In any case to insert a horizontal rule I know of two methods...
1. Type three consecutive dashes "---" at the beginning of a line and press
enter.
2. Select "Format|Paragraph", then the Borders tab, pick a top or bottom
border, a line style width and color and click OK.
Method 1 has the disadvantage that every subsequent paragraph gets
underlined and so the format must be disabled on subsequent paragraphs.
Method 2 suffers the same disadvantage if the border is specified as a
bottom border. However if a top border is selected it is not applied to the
following paragraphs.