I made the mistake of having different hostnames for the "view" and "input comments" parts of this weblog, so if you're writing comments they might go to the old server while DNS updates are propagating ,and not be visible. I'll fix this tomorrow once all the DNS stuff has gone through.

Apart from that, copying the Movable Type files to the new server didn't work as the Berkeley DB files were incompatible between my old redhat and new debian systems. Converting the MT database to MySQL on the old server (as described here) solved the problem.