You can ovveride default wall method search / listing posts paramter for method OssnWall->GetPostByOwner()

Working example is OssnBlock component that trims posts from newsfeed if user is blocked.

<?php
function my_component_init(){
		ossn_add_hook('wall', 'GetPostByOwner', 'my_component_hook');	
}
function my_component_hook($hook, $type, $params, $extra_params){
		//you may alter $params , it contain order_by, etc.
		//$extra_params contain $extra_params['owner'] which is GUID for user
		error_log(print_r($params, true));
		error_log(print_r($extra_params, true));
		return $params;
}
ossn_register_callback('ossn', 'init', 'my_component_init');