I think developer knows the problem because of the language. I'm a german developer and prefer to describe my plugin in german. It's easier and more comfortable to read for german users.
But I want to share my plugin(s) with other people, too (England, France,...). I myself could write a description at least in 2 languages.
It was very useful to integrate a feature for multilingual readme's. For example readme_de.txt or readme_en_US.txt.
A possible fallback could be a standard readme.txt.