I used the same method to import the text from an ascii file: <ctl>-c and <ctl>-v. Sometimes it double-spaced the lines. Other times it single spaced them. I "inspected" the page and I see that there are <p>...</p> around each double spaced line, so the editor thought that each line is a paragraph. The single spaced lines are all within a single <p>...</p> and have <br> between them. There are no blank characters at the ends of the lines, and no tabs in the lines.
How can I either convert the double spaced text to single, or import it in a way that makes it single spaced?
I tried <ctl>+<shift>-v and <cmd>+<shift>-v, but neither helped. Removing the blanks at the beginnings of the lines doesn't help.
More abstractly; why does the editor enable me to control horizontal spacing several ways, but no way to control vertical spacing (other than empty lines)?