Final update: the broken logo image is no more. I finally tracked the faulty html down to the Weaver Xtreme theme settings and removed it once and for all. Goodbye, little question mark.
Update: the hosting migration appears to have gone smoothly. DNS change propagation should complete within 1 day of this post.
(And yes I am aware of the broken logo image at the top left. It resulted from reloading Weaver Extreme Plus settings after migrating the database, causing the old uploads directory URL to be used. I will fix it after getting some sleep, and finding time to do it. On second thought, I kind of like it so maybe I will keep it.)
The site will be up and down and otherwise wonky for a while. It will be back to normal soon…