There are a couple of copies of Cari Mora on eBay right now that have pictures of the signed page - there are definitely some small differences between the two, most notably the loop on the "h" in "Thomas". Also there are darker marks where the strokes would start and end and I don't believe autopens do that.

https://www.ebay.com/itm/Cari-Mora-b...MAAOSwiFZc4B9O

https://www.ebay.com/itm/Cari-Mora-b...sAAOSw3rJc5a--

FWIW Harris does have a very neat and consistent signature.

I'm still waiting on my copy but my current vote is that they are real sigs.