Try enabling it on the Tarski Options page. It’s listed under Sidebar.
It’s a great question, but I think the answer is to move the comments up! is there any way to put the comment form under the last post, other than by inserting an add-on form of the kind that never seem to go with Tarski. I think your point is so interesting and might explain why I’m getting healthy traffic but zero comments… visitors can’t find the box, or don’t realise that each shorter page still has one at the end.
Please add on to this if you find a lucky solution.
Comments have moved directly under the content in the latest version.