I'm not sure why it's such a big deal to have separate Traditional and Simplified versions of pages on Commons. Unlike most other projects, language is obviously not a main concern of the project, that's why it combines so many languages in one site.
The automatic converter for zh.wp is not perfect, in fact it has many problems. However, on zh.wp, there is a huge volume of material written in Chinese, and to publish separate editions would be such a divisive move that it is much less practical.
With Commons, on the other hand, the only sorts of material that need to be translated are things like documentation, a relatively small volume, so the effort to convert by hand is not misplaced -- why not have a better-quality product when it takes only slightly more effort?
Mark