I didn’t change servers, I just changed which domain name the site was using. I did, however, replace all references to the old domain name. It’s a little troubling, as I don’t want this to continue happening. I will try reimporting everything and see if it retains the history.
As for the “Undo,” I thought you’d suggested to me elsewhere that I could use this as a way to wipe the slate clean. That’s what we want to do each time we do an import. Deleting existing posts via the regular admin is time-consuming when you have 2000 records… Do you have a different solution for deleting en masse?