Due to an attack by a comment spammer, I regret that I have suspended all commenting to posts here.

I hope to resume them later, when the spammer has poked off to annoy someone else.

Update 1900 GMT 18 May:

I have now opened up comments again on recent articles, and they no longer require you to be logged in. For the moment, though, I will moderate all comments before they appear here, to ensure no more spam is posted. This may lead to slight delays: please don’t send multiple copies, though. Any that are posted overnight (roughly 2300-0600 GMT) will have to wait until I’m awake the following morning. I apologise for this, and will continue to ease restrictions as much as possible.

Thank you for your patience and support.