Comment 46 for bug 292473

"I don't understand why Canonical claims that a fix has been released."
The problem stated in this bug that brought about a massive lack of translation was a bug in Launchpad that caused strings with context information or plural forms to not be imported. The software *has* been fixed to this point and translations with context info or plural forms *are* being imported by Launchpad. You can see for yourself: https://translations.launchpad.net/ubuntu/jaunty/+source/kdebase/+pots/dolphin/es/+translate

The first string there "Empty trash" has context information right below it. It's existence on that page shows that this bug is indeed fixed and that the upstream translations that include context and plural forms are, in fact, being imported.

Which brings us to your comparison. Regardless of whether you are using the KDE 4.2 packages in Kubuntu 8.10 or Kubuntu 9.04, both are using the language packs from Kubuntu 8.10, which are in turn based on the KDE translations for KDE 4.1. As strings have changed since KDE 4.1, the translations included in the KDE 4.1 langpacks become outdated and useless in KDE 4.2 where new, different strings are in place.

As translation focus has only very recently shifted to Kubuntu 9.04, no lang packs have been generated for it yet. Once they are, most of the untranslated strings you are seeing due to the old langpacks should be gone.