We use mantis as our bugtracking system and I had such problem:

When entering view_all_page during customization user can wiew other users and support team logins (in "addressed to" or "reported by" lists). We created some logins with company name f.e. b_gates(microsoft), so we don't want other users to see that. My boss also told that this filter options are to complicated for our users. I changed a little bit in filter_api and added one variable to config_inc.php. If you find it a good solution please add it to next version.

By the way - great job, guys.