Source

File: wp-includes/comment-template.php

function get_comment_excerpt( $comment_ID = 0 ) {
	$comment = get_comment( $comment_ID );

	if ( ! post_password_required( $comment->comment_post_ID ) ) {
		$comment_text = strip_tags( str_replace( array( "\n", "\r" ), ' ', $comment->comment_content ) );
	} else {
		$comment_text = __( 'Password protected' );
	}

	/* translators: Maximum number of words used in a comment excerpt. */
	$comment_excerpt_length = intval( _x( '20', 'comment_excerpt_length' ) );

	/**
	 * Filters the maximum number of words used in the comment excerpt.
	 *
	 * @since 4.4.0
	 *
	 * @param int $comment_excerpt_length The amount of words you want to display in the comment excerpt.
	 */
	$comment_excerpt_length = apply_filters( 'comment_excerpt_length', $comment_excerpt_length );

	$excerpt = wp_trim_words( $comment_text, $comment_excerpt_length, '…' );

	/**
	 * Filters the retrieved comment excerpt.
	 *
	 * @since 1.5.0
	 * @since 4.1.0 The `$comment_ID` and `$comment` parameters were added.
	 *
	 * @param string     $excerpt    The comment excerpt text.
	 * @param int        $comment_ID The comment ID.
	 * @param WP_Comment $comment    The comment object.
	 */
	return apply_filters( 'get_comment_excerpt', $excerpt, $comment->comment_ID, $comment );
}