Hello
I've just had to hack the Jetpack Comments module. (Which I don't like doing because when you realise an update it will get overwritten)...
However when you do update the plugin PLEASE PLEASE PLEASE can you update line 250 in /modules/comments/comments.php so as to include the $params['greeting'] variable. There's no point asking for it, if you're not going to use it! ;)
<h3 id="reply-title"><?php comment_form_title( __( $params['greeting'] ), __( 'Leave a Reply to %s' ) ); ?> <small><?php cancel_comment_reply_link( __( 'Cancel reply' ) ); ?></small></h3>
Thank you! :)