Never moderate or mark as spam comments made by registered users, regardless of the apparent spamminess of the comment.
This plugin prevents comments from registered users from ever going into the moderation queue or getting automatically marked as spam, regardless of the apparent spamminess of the comment.
To be recognized as a registered user, the user must be logged into your site at the time they post their comment.
This plugin assumes that you trust your registered users. It will automatically approve any comment made by registered users, even if the comment stinks of spam. Therefore, it is recommended that you do not allow users to register themselves (uncheck the setting "Anyone can register" in the WordPress admin under Settings -> General).
You can still allow open registration, whereby these "subscribers" as moderated as usual, while other more privileged users do not get moderated. The plugin provides a filter, 'c2c_never_moderate_registered_users_caps', which allows you to specify the roles and capabilities that can bypass moderation. See the FAQ for an example.
This plugin is a partial successor to my now-defunct Never Moderate Admins or Post Author plugin. In addition to preventing admins and the post's author from being moderated, that plugin also allowed you to prevent registered users from being moderated. WordPress has long since integrated that functionality, so the main thrust of that plugin became moot. However, the ability to never moderate registered users is still a valid need that requires this plugin.