Keyboard shortcut please !
List of current shortcuts : (http://www.duolingo.com/help)
If you have the time and it is not very complicated please add one more just for opening the sentence discussions in the lesson.
I remember one of the older posts from a member of duolingo staff stating that you want to make duolingo completely mouse free. :)
I try to open each and every comment section when doing a lesson even if I don't need any help just to check if somebody else needs it. This way it is a bit bothersome because of constant switching between mouse and the keyboard.
Also when you close the discussion section (by pressing Esc or clicking the x button) and then press Enter in order to continue to another sentence/exercise it will reopen the comment section.
I was thinking of suggesting another keyboard shortcut for report problem but I figured it's better not to because switching from keyboard to mouse actually gives people a bit extra time to rethink if that is really something they need to report.
Probably there are some other ways but I use different keyboard layouts and it works fine for me. That means after adding other languages to my language bar I can easily switch between them by pressing alt + shift.
Here is the link that explains how to change your keyboard layout : http://support.microsoft.com/kb/258824
Also I used microsoft keyboard layout creator because I wanted to make custom keyboard layouts (rearrange the letters as i saw fit :) )