What is the little up and down arrows with the numbers by it on the discussions in the bottom left corner?
It is away of showing if you like or dislike a post. The up arrow says you like the post, the down arrow says you dislike the post.
PS posts receive 5 or more down votes the are hidden from view in the forum. It is also possible that moderators can delete these posts if they feel that they go against Duolingo's guidelines.
Upvote and downvote buttons. Upvoting is for comments that are useful, downvoting is for posts that are off topic, spammy, or in the wrong place.
its if you like a persons comment you can like(upvote) it and in the right corner you give a lingot to the comment author
ohhh! how come sometime if you click the up or down arrow it goes up or down by 2?
Sometimes people just down vote a comment because they think that it is fun.