If you read the comments on a problem, and while doing so, click on to the commenter's profile to see if they know what they're talking about, when you go back to your lesson you've lost all your hard won progress and gone back to the start. Is that to keep people from being nosy?
It's the same with reading discussions. If you click on a discussion and press return, you are brought back to the top of the discussion list; not the place where you clicked the link. I use tabs for nearly every link.