extern.php restrictions?

Ive been playing about with extern.php and have to say I think it is brilliant, and so simple!

I do have one worry however and wondered if there is a simple code to get around it. When a user posts a message on the board it obviously comes up on the front page of my site, but what if some asshole registers and post links to porn etc (something I dont want my site advertising). Is it possible to only show latest messages from "trusted" members? I see two solutions but maybe both wrong?

1. I believe I would could make a usergroup for "trusted" members and somehow call that on my sites index.php

2. Create a second forum, read/replies only, and only call posts from that forum to the front page. Trouble is I want to have an open community, with all members contributing to news and discussion. I dont want to limit 'news to forum 1' and 'discussion to forum 2'

Im still learning PHP so hope someone can show me how to get around this.

Thanks,
Will