Hi Leo,
You could use HTML tags to apply a style to a portion of your text. Usually browsers render <em> as italics, and the tag <i> is sort of deprecated. The most reliable, universal solution would probably be <span style='font-style: italic;'> like this:
newText("practiceinstructions", "We would not typically describe this scene using this sentence, because \"at least two\" leads us to expect more than two apples. You should <span style='font-style: italic;'>not</span> rate it as 6 or 7.")
More generally though, when you want a trailing white space, you can add a non-breaking space using
Jeremy