Here’s the problem: Akismet is marking valid posts as spam when behind a load balancer. Because of marking comments as spam when Aksimet sees the IP address as coming from your load balancer, and then any comment that comes through gets marked as spam.
WordPress has quite a few hidden features. My favourite so far: MU Plugins, or “must-use plugins”. Introduced with WP 3.0, the code says:
* Check the mu-plugins directory and retrieve all mu-plugin files with any plugin data.
* WordPress only includes mu-plugin files in the base mu-plugins directory (wp-content/mu-plugins).
* @since 3.0.0
* @return array Key is the mu-plugin file path and the value is an array of the mu-plugin data.