When clicking 'discuss sentence' in lesson, automatically open in new tab/window.
Not for the first time, I accidently navigated from a almost complete lesson because the links in the 'discuss sentence' popup, do not automatically open in a new tab/window, and I forgot to manually do it. And of course, hitting back, returned me to a lesson with 0 progress.
I know this could be put all on the user, but if we are talking about user experience, and small change, then this fits. Since the url in a comment/post is automatically changed to a link, its easy to put in the code to make it open in another window.