Idiomatic phrases in different languages.
I think that could be a good idea to create a list (maybe in google docs) about idiomatic phrases, I don't know if already exist something like that in any website, if it so, please write it down, otherwise may we can create one. What do you think? could be a good idea? or it just useless?
There are so many idiomatic phrases that this could be quite impractical. There is a book on my shelf which contains Idiomatic phrases just from the English language. It is quite thick with many thousands of phrases so multiply that by the number of languages currently taught by Duolingo and it would be a huge document.
Not only that, if you take English as an example, there are so many idiomatic phrases that are particular to one country that it would be confusing. And within countries such as the United States there are idioms particular to a region.
Maybe we can focus in particular cases as expressions, ways to say hello, etc. It's just an idea. However from your point of view.. you are right.