Note that I'm not talking about TypePad, but TypePad Connect, their hosted commenting product. I see comments in their company blog from 2008 (!!!) saying they were working on an export feature, but I don't think it ever launched. So... is there any way to get old comments out of a TypePad Connect system? Or are they trapped in there forever?
I determined that there is no automatic way, and no way to export comments from TypePad Connect.
I ended up creating a very tricky hack that slurps all the comments from TypePad Connect. (In turn, I put them in XML format and was able to import them into Disqus, which is the commenting system my client turned to.)