I’ve determined that in order to completely wipe all your Movable Type entries, comments, categorizations, trackbacks, and sent pings, while leaving configuration and templates intact, you need to truncate only the following tables in your Movable Type MySQL db:
When that’s done, you have a virtual tabula rasa, into which entries, comments, and pings can be re-imported — assuming you remembered to export them from MT before embarking on this foolish endeavor of renumbering archived entries chronologically, under one category.
(Also, when importing entries into Movable Type from a text file, don’t hit Stop. It keeps going even if you try to interrupt the process, and if you try to do an import again while that’s going on, you end up with duplicates of everything. A long, slow process when you have 2,420 entries and over 3,300 comments.)
Soon: thoughts on WordPress.