I don't get it. How does sending a postcard to a site confirm your identity? I can understand the site sending out a postcard with a verification code on it but for the user to send in a postcard doesn't seem to make sense.
Besides that it looks like an interesting phenomenon. Simply increasing the latency of posts would probably improve the quality. With no instant gratification many trolls simply wouldn't bother posting.
This seemed flawed to me, "To post opinions in the Tsukurepo section, advance approval from those who introduced the recipes is necessary." I bet all the reviews are raving. Seems like a nice way to stifle differing opinions.
Never been to Japan, I must have read it somewhere, so reader beware.