WordPress at a glance
filter is not described

comments_clauses filter-hook . WP 3.1.0

Filters the comment query clauses.

Usage

add_filter( 'comments_clauses', 'filter_function_name_1576', 10, 2 );
function filter_function_name_1576( $pieces, $this ){
	// filter...

	return $pieces;
}
$pieces(array)
A compacted array of comment query clauses.
$this(WP_Comment_Query)
Current instance of WP_Comment_Query (passed by reference).

Where the hook is called

WP_Comment_Query::get_comment_ids()
comments_clauses
wp-includes/class-wp-comment-query.php 855
$clauses = apply_filters_ref_array( 'comments_clauses', array( compact( $pieces ), &$this ) );

Where the hook is used (in WP core)

Does not used.