SSLab's grades are not stupid. They monitor how solid the SSL implementation is and what needs to be corrected to ensure higher security on the site.
Another useful tool is SSLScan, which for Hacker News shows that they are accepting of a very strange set of HTTPS cipher and MAC configurations.
SSLv2 should be turned off, as well as the majority of 40-bit and 56-bit ciphers. Their unusual preference of CAMELLIA-256-CBC is pretty amusing to me.