Create a thread and use it as reference if you have more to say than what fits into the 5 ratings. Keep in mind that multiple ratings from the same person count only as 1 in the score, so 1, 5, or 25 wouldn't make any difference for a casual observer, but if someone wants to read more - they can follow the link.
Agree, but the OP will decide for himself the best way to document his trading history with other users. I don't think it will take much ratings for one user for every successful trade. If the OP has a thread that is constantly being updated on its trading history then 1 ratings in my opinion is sufficient to represent its trust in one user who has successfully traded with it. It's just that the OP need to add a little description like "managed to make 25 smooth trade with this guy, check reference for more detail". Looks good to me.
I also just found out that a person can only send 5 ratings to the same 1 user profile. But do positive, neutral and negative count as 5? I mean, for example I have sent 2 positive ratings, 2 negative, and 1 neutral for one user. Can I still do the 6th for the same user?