Da dieser Artikel nur ein sehr kleines Zielpublikum haben wird, verfasse ich diesen auf Englisch.
During the last weeks I migrated three old (I should rather say very old) installations of Movable Type to WordPress. For the younger generation: Movable Type is one of the first blogging systems which came out long bevor WordPress was published.
For this process I created some SQL code which migrates more information between the systems than a regular export and import would do. It still covers not everything but you can easily extend it for your needs. For newer versions of Movable Type you might also need some changes.
The method will transfer posts, comments, categories and tags from Movable Type to WordPress. It is based on the assumption, that you only use one author. It works for German special characters when it comes to the slug. You can run this SQL code multiple times, because it will delete all existing database entries.