Many, many forums use a feeble ratings/trust indicator for pseudo-anon users but then you end up with a clique of highly rated posters and the circle jerk is complete. The whole point in anonymity is every post has it's merit in what it says not who wrote it. I can easily skim the various *chans, filtering out shitposting pretty quick.

For trading pseudo-anon there is already this reputation system which has worked well http://bitcoin-otc.com/trust.php