Native vs Second Language to a Third Language
Some of us are already bilinguals or multilingual, and we can provide feedback, help on our original/native language. Our profile only allows to enter: one spoken language and the one being learned. Unless I am looking at the wrong area..
I second! I would be delighted to exchange my Spanish for other languages (currently, German). Students can dramatically boost their knowledge by being more social and sharing their languages. Several 'match-making' on line services do this already. This looks like a whole new area to be developed in duolingo.