Sort within a Discussion by popularity and newness
It took me running into it a few times before I realized that within a given discussion post, comments voted up the most trickle up the list. This is a good feature, of course. However, equally important is being able to sort by how new comments are, for when you are returning to an ongoing discussion hours or days later. There is no way (that I know of; if there is, please point it out) to see the newest posts currently, because something could be new, or simply not upvoted. The suggestion is there be a sort selector (like there was for vocab). ...(Oddly I cannot hit Enter within my post right now, so no new paragraphs. Chrome latest.)
At present there is no user sorting of any kind except as provided by the tabs (popular/new/top alI-time) and indirectly through voting. I once suggested an "active tab", I particularly wanted it for sentence discussions although the idea would work with user discussions too. See: http://www.duolingo.com/comment/633086.