This function had been marked as deprecated.

Formerly used to escape strings before inserting into the DB.

Has not performed this function for many, many years. Use wpdb::prepare() instead.

Signature

format_to_post( $content )
content
 (string) The text to format.

Return

(string) The very same text.

Source

function format_to_post( $content ) {
	_deprecated_function( __FUNCTION__, '3.9' );
	return $content;
}
WP Trac GitHub

Link here