An interesting idea - but the truth is that far fewer people would bother reading the content of anybody below a certain threshold of English proficiency. It is already tough enough to get people to (actually) read the content of the best posters out there without simply tossing their up-cote for "curating" purposes.
I personally believe that the message is more important than the language that it is delivered in. In other words I consider the meaning above all else. Which is not to say that the effectiveness of delivery is not important - as such clearly is.
The challenge inherent to your suggestion is to overcome the tendency for such articles labelled in such a way to simply be overlooked on the basis of such. Some messages are better-delivered by other Steemians - but this is not true for all messages - and some may well be too important to be lost to such labeling alone.
Still - keep on thinking! :c)
Maybe so. It could be separated by country though. It seems to me that people from all countries would appreciate that, if they had a place to go directly to, to see posts in their own language. I see what you are talking about on the rest of that though.
They have country tags to help with that... :)
Perhaps a simple way of expanding current functionality is to simply allow an extra tag which must derive from a list of country tags. It would be great for contextualizing posts - but not necessarily determine what level of English proficiency one is to expect within.