[Jetpack] Add the category name before the Publicize message More details: here: http://wordpress.org/support/topic/jetpack-publicize?replies=18#post-4836869

plugin.php

<?php

// Create our custom Publicize message
function jeherve_cust_pub_message() {
	$post = get_post();

	// Grab the first category of your post
	if ( !empty( $post ) )
		$categories = get_the_category( $post->ID );

	if ( !empty( $categories ) ) {
		$previous_cust = get_post_meta( $post->ID, '_wpas_mess', true );

		$custom_message = $categories[0]->cat_name . ' ' . $previous_cust;

		update_post_meta( $post->ID, '_wpas_mess', $custom_message );
	}
}

// Save that message
function jeherve_cust_pub_message_save() {
	add_action( 'save_post', 'jeherve_cust_pub_message', 21 );
}
add_action( 'publish_post', 'jeherve_cust_pub_message_save' );