I have no problem with people choosing to use something other than :MT: when they blog (because different packages work better for different people, same thing goes for OSen, browsers and editors -- I totally get that), but dammit if it doesn't piss me off when I go to leave a comment (from the laptop) and I get the "you can't post comments from your laptop because it doesn't send some information that I need, sucka" error message. I almost never go back and leave a comment on those posts when I am on my PC later.
So :p to whatever cofiguration option causes that.
Update: More information error message from a friend:
Error: One of the WordPress spam-prevention systems is not letting you post because you did not send at referer (sic) header. Some firewalls block referers for privacy reasons. WP requires a referer because some comment spammers do not send it. So, either turn off your firewall for a bit, or whine about it on LJ ;).
Actual error message:
Error: This file cannot be used on its own.
[A Geek in Beantown] (Permanent link to this entry and comments from non-LJers)

Comments
New error message for the curious:
"Error: One of the WordPress spam-prevention systems is not letting you post because you did not send at referer (sic) header. Some firewalls block referers for privacy reasons. WP requires a referer because some comment spammers do not send it. So, either turn off your firewall for a bit, or whine about it on LJ ;)."
(And I'd been trying to comment on another site this time, so it's not only you guys.) :)
Distilling down that thread as best I can: WP installs configured to use a popup window for comments are subject to this error, under what appear to be varying conditions. The trick is that the popup script is checking for its referer (which, of course, should be another document on the blog) and bailing when that referer data isn't there (because it thinks that someone's trying to call the popup page directly).
Not that I have a solution for this, mind you, but maybe this will help someone cleverer than myself to do so. I don't use the popup window method, myself, so... *shrug*