Well, that was interesting. The most recent upgrade of Jetpack for WordPress caused the “Post Comment” button on the Jetpack comments to stop working. In short, WordPress nadgered my wordpress blog!
In order to get the comments working again I had to deactivate the entire Jetpack plugin, clear the cache and then reactivate the plugin, including re-registering the plugin, and my blog with WordPress.
It was all very exciting and completely superfluous as baring one old friend, no body but me has ever left a comment on the entire blog.
Go on test if my fix has actually worked, and post a comment.