There is a script to move from s9y to wp online. This stopped after moving all the posts but comments stopped at 2007, and categories and comments weren’t linked. If I understand it right, Trevor succeeded in moving the rest by clearing out a lot of stuff from the databases, emptying things like spam comments from tables to reduce the amount to be migrated. Even the images came over, which I wasn’t expecting, but this was probably down to coding work on his part.
I’m hoping that if I get a wave of spam comments which the blog fights off, it won’t shut down the server again like it has done twice in the past. The system looks easier to use. It looks as if I don’t have to do so much by hand on an upgrade. Serendipity was in bad English (domainfactory offers an instant wp install, into bad German). I should probably write down all the steps for customizing the blog, since my brain doesn’t seem to retain them.