There is a new version of PHP "SmartyPants" called "PHP SmartyPants Typographer" which extends the functionality to handling the non-breaking spaces and double-quotes.

For me the second part in quite more interesting, because here in Poland we are using german-style quoting („example”) instead of english-style (”example”)... and probably greek uses it differently (”example„).

Additionally it will be fine, if it could be node-locale sensitive, but it is less important - it could be developed later.

I do not have enough time to configure system for drupal development, because I could prepare a patch then.