I'm very sympathetic to policies designed to combat spam. It's pretty grotty stuff. Surely there are better ways, no?
Couldn't users be required to fill in a captcha for the first 20 messages or something? This unusual policy is a high barrier to entry for legitimate potential members of the community.
This anti-troll policy is arguably great to prevent existing trolls from joining the forums. But I put it to "you" that it might create more trolls than it filters!