When shading paragraphs, word shades from the left margin to the right margin of the current paragraph?

This statement is true. It makes more sense to shade this way since the words typed on a computer start from the left and go to the right as more words appear, which is just how writing on notebook paper works. Doing it from right to left would be more uncomfortable for the user and require them to shade words potentially going up and right instead of left and down.