wordstogoodeffect on "[Plugin: Jetpack by WordPress.com] Suddenly getting problems with Jetpack comments"

Thanks. I don't think Askimet's the problem, it's just that the comment posting problem arose at the same time as I re-activated Askimet.
When I (or my users) click on "comments", they're just returned to the post, ie the comment form simply doesn't show up. It's not a question of comments being marked as spam.