anomaly in highlighting pdf

AFter highlighting two lines in a pdf, using the toolbar icon, I decided I wanted to make one word stand out by highlighting it in a second color. When I selected the one word and used the menu format >highlight color > to choose another color for that word. The word was highlighted in the chosen color but the rest of the line became un-highlighted.

If, then, I select the entire line and use the toolbar icon to highlight it in the original color, the line (including the word highlighted in color #2) becomes un-highlighted.

It appears that highlighting is first a toggle on/off option, and secondarily a color-choice option. Changing the color alters the state to “off”. Or to a non-programmer it seems so…

A further anomaly is that despite using the standard Apple UI element of double-clicking and dragging to select entire words at a time, it is possible to select partial words, as below:
DTP post.jpg