I noticed some people having trouble leaving feedback. This is the way to do it so the trade count you see under the persons name will go up.
First what you will need to do is go to the persons profile:
I used Dalamar's since we all know and love him
Next, click on the feedback button:
Then click submit feedback for ____________, in this case, it's Dalamar
That will take you to this screen:
After that, it's just like leaving a normal post, with a few options to say how the experience was.
Hope this helped, now leave some feedback!