I just pushed the left button on my mouse and, holding it down, passed it over the above sentence. That "selected" it and "highlighted" it. When I clicked on reply all that got transferred to the reply window was the highlighted text and the when and whom line.
If you mean I didn't physically run a highlighter pen over the screen then you're correct :-).
I'm using the Pan newsreader under Linux. Under Windows I would use Free Agent.