If the «closing quote replacement« fails in all cases, it’s likely a translation issue and not wptexturize itself. If it is due to an unusual situation where open/close gets out of sync, it may be able to be corrected through the $wp_cockneyreplace global. The normal example in English is where apostrophes used in the spelling out of Cockney English words will mess up normal curly quote replacement, like "'tain't" => '’tain’t'. This mechanism can be used to define any unique replacement not properly handled by the normal texturize routine.
There are filters available to manage which HTML tags and shortcodes are omitted from being texturized, but there is no generic filter we can use to override anything the function does. We can turn it off so nothing is changed, but not override by using filters applied within wptexturize().
What we can do to override is add our own texturize function to the same filters where wptexturize() is added. Add with a larger priority argument so your callback executes after wptexturize(). Your callback can search out instances of «flipped« closing quotes and «fix» them, for example.
The most common filter to which wptexturize() is added is of course “the_content”. There are a number more. Dump out global $wp_filter to find the rest.
If there is a persistent issue with how wptexturize() works, consider filing a Trac ticket documenting the problem. If you can also offer a patch for the problem, the speed of getting the correction committed to core code is increased.
