I have tried to post these two comments in different places but have not got any official answer: 1. several of the texts we are asked to translate from Spanish into English (in my case) are translations of an original English text, as for example Oscar Wilde's Happy Prince. I see litle point in putting our poor prose in place of Wilde's scintillating creation and especially since there are so many articles written originally in Spanish. 2. I was recently invited, in the Real world practice section, to work again on an article on Flaubert, to which I had contributed to about a month ago and which was already on its way to being completely translated and in great shape. But now it was submitted again at a very rough stage with many words still in Spanish and in very choppy English. Perhaps I misunderstood what I thought was DL's intention to use all of us to translate the web. Do they restart texts from scratch?
Anyone can submit a webpage to duolingo for translation (provided that copyright rules are followed) and while the submission queue is moderated, it is done with a fairly light touch. However, there is the opportunity for immersion users to downvote articles and while downvoting should be used sparingly, the 'bad' submissions you describe would, in my opinion, deserve it.
I especially agree that re-translating a document that is already a translation from the target language is a fairly pointless exercise. I downvote these submissions when I see them.