Gonepostal: Test the process this way... does eBay allow you to leave any feedback for anyone who you have not actually executed a transaction with? Absolutely not, no transaction took place so there is nothing to render a judgement on. The Trader Rating system here is based on the eBay system by design and intent. Work the logic backwards.
Because the d-board does not actually control the transaction itself, it can't know if two people have executed a transaction and thus the feedback system is left open, so it is left up to the buyer and seller to manage the feedback appropriately.
I get about 2 to 15 emails/PMs a day for buying. I do my best to get back to everyone in a timely manner, but, sometimes I don't and it takes someone a second email to remind me to get them a quote. I've *never* had anyone leave me negative feedback on that basis - its understood I am using my best effort and if a buyer does not receive a response from a potential seller on a query, its pre-purchase, and its understood that the buyer can choose to shop elsewhere if they feel underserviced. But it is NO basis for negative feedback.
If I was a mod, I'd not only reverse that negative feedback but also educate the person who left it on how the trader feedback system is meant to be used. If they continued to leave others negative feedback without sales, I'd suspend their account privledges on the basis of abusing their privledges.