After successful installation of WP-Cache, I’ve encountered another problem, that’s the compatiblity issues between Spam Karma 2 (SK2) and WP-Cache. This issues led me to Priv’s SK2-WP-Cache-Compatibility plugin which sucessfully fixed the case of the missing comments.
When you use Spam Karma 2 with WP-Cache, cached files are not flushed after a successfully comment approval. That’s basically because SK2 intercepts some actions, WP-Cache will not get notified. Priv had created a small plugin for SK2, that will directly call wp-cache to flush cache, after a comment is approved.
Download this zip, extract and drop the php into sk2_plugins directory, it should just work.
More info: Plugins Page