Thanks @AlyssaWOAH, but I figured why I was having trouble. It was a conflict between my browser and this forum software. My browser, (Opera), pops up a "Search | Copy" box, similar to the forums "Quote" box. But Opera centers it on the selected text. So, depending on how much text I select, the Opera box will cover the forum box. In the following image are two segments of two screenshots that I took. The top half shows me selecting a small portion of text. The Opera box covers the forum box. (You can just barely see a bit of the forum "Quote" box above the Opera box.) In the bottom half of the image, I selected a longer line of text. Now you can see both boxes.
This was a bit long-winded, but maybe it will help someone else who might experience the same browser behavior.