I received this from Disqus tech support this afternoon:
The reason why these comments from Echo aren’t importing is because they aren’t given a URL to link the comment to, unfortunately. We’d love to be able to offer a way to bring them in, but for now it’s not possible with this format. We’ve opened a ticket with our development team for any possible ideas of how to do this, but it’s still in the planning phases.
We’re sorry for any inconvenience, we know it’s important to import your existing comments, so hang onto those files.
Thanks again for using Disqus
So apparently the export files from Echo/JS-Kit don’t have identifying tags that Disqus can recognize. But Chris Byrne was able to successfully import his comments. I’m alone in having fvcked-up export files?