In order to translate messages, I had some adjustments to make:
- create po/mo files in order to translate the messages.
- edit wp_inline_comment_errors.php and specifiy a high priority (1)
- edit wp_inline_comment_errors.class.php and move the messages array definition array in a plugins_loaded hook with a low priority (10).
There were lot of warning and errors (I have WP_DEBUG set to true). Fixes were easy, usually "global $wp_inline_comment_errors;".
Great plugin otherwise, much needed to prevent the default WordPress error comment page.