Anton said he wanted a way to get all his comments in one OPML file. He didn't say it exactly like that, but that's what I see as the first step down a good path to take.
So I tried literally just writing out the OPML from the Comments Workspace, and it wasn't right. There are many attributes on the top level node that make no sense in a display context. Rather than try to adjust the server, I commited to doing a bit of surgery on the content on its way out. It's very lightweight stuff compared to some other stuff I've been working on, so I know how to do it.