I just notified duoLingo that I thought my answer 'They are not arriving' should have been accepted. However, I have a question regarding this:
If I am unsure if I think the answer is wrong / right, is it better to post the question to the conversation ( ... or in this case my 'whining' that I think my answer should be correct ;-) first, and wait for an answer on the board ... or to report it to them and not post? I would hate to waste the moderators' time with anything erroneous; I am the one learning the language ;-)
(I was astounded to find out there are only about 30 people running duoLingo ... bravo!)
Sometimes an answer may not be accepted but after a few reports it is added so one person got it incorrect but later it was considered correct. So, let's not forget to report when we think something should be accepted, or changed. I've just seen a message from Duo saying:"we are working on the quality of the Italian listening."