Blitzed ceased operations
Perhaps you experienced some delays in commenting. Well that was caused by the spamfilter. Or actually caused by the fact that one of the blacklists (blitzed) ceased its operations, causing the filter to look up the IP and never got an answer.

Installing The Spamhaus project
Now there is a new blacklist which can be installed. It is The Spamhaus Project. You can find more details how to install it in you spamfilter on the page of SixApart.
Just removing and adding a line and that’s it. Commenting should be to its normal operation right now.