Because of ongoing high-volume attacks on this blog by comment spam, I regret that I have had to disable commenting on older articles for this weekend.
I apologise for this, but I’m currently having to deal with hundreds of spam comments every day, which is taking up a lot of my time.
You are still very welcome to add your comments to articles which have been published more recently – that still works normally.
I hope to remove this restriction in a few days.