Although it would prevent feedback spam, if we keep doing successful trades it does limit what can be said about other users.
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 and if someone wants to read more they can follow the link.