Recently a number of blogs (British ones in particular) have gotten Draconian about comments.

I've thought about this a fair amount - my new criterion is that I will delete comments that in my view encourage discussions of the sort that most people won't want to read.

Update:

I have realized that I opened a real can of worms by considering comment moderation, and that I don't have the time or will to deal with it. Hence the new blurb at the top of the comment box says that comment moderation is up to you the commentor.

I'm grateful to the person who suggested open threads for ongoing general debates, and hope that as a consequence there will be informative on-topic discussion on the regular threads.