I think this could be a good idea to see how qualified or trustworthy somebody is, and also be able to be rewarded for other things than trading. This could have the effect people think more about their post and about what they have to contribute. Maybe make them put up some tutorials since it gets them reputation/status and not let them post stupid things other can irritate themselves about since it could give them a negative rating.
You could do this in several ways, these are a couple I have toughed of. And also a couple I forgot since this isn't the first time I had to type this.
Firstly a very simple rating system, thumb down, thumb up. This could be done on user basis or post basis. If you choose to rate the user it could be easily be put under the iTrader with a thumb up, thumb down and a total score.
If you choose to also relate it to the certain post I would also put a small section under the post with how much the person got thanked/rated. Or how many user liked the post. Also posting a section on the profile and/or with around the iTrader section. Rest could be used the same. =)
That brings me to the next option. Add a small option to thank a user for his post. Also add a small section under the post if the user is thanked.