As at May 21, Typepad (our blog hosts) instituted a comment spam blocking system. The details are here.
Unfortunately, the nature of the blocking has a distressingly large number of false positives. It seems that if your IP address falls into a range that has been allocated to a spammer previously then you're blocked. Since lots of spammers use ISPs with DHCP there is a non-trivial chance that the IP address you're coming in on now has previously been used by an "evil doer", and so you may be blocked. Some of our best friends have already expeienced this problem. Typepad note breathlessly in their comment that "on our first day [the spam block] blocked over 20,000 spam attempts!" And they could distinguish these spam attempts from legitimate comments how, exactly?
We're currently in negotiations with Typepad to get this thing fixed. If they don't work out a fix bloody quickly then you can expect a note here directing you all to a better blog host.
In the meantime, if you can use the comment fields of this message to let us know of any problems you've had in commenting, then that'd be helpful. And yes, I know that if you are blocked from commenting then it's going to be hard to comment here. But if you wait a while and try again you may find that your IP address has been reallocated, and you're on an address that hasn't been blocked. Or borrow a friend's machine. Or do some wardriving and find an open ssid (there is one outside my house in Chestnut Hill, Philadelphia in case you're passing by). Do your best.
Thanks. And our apologies.