I guess I answered my own question!

Looks like they are not refundable. I had to go half way through the purchasing process to find this out though.
Here is the official notice from the ticket ordering website:
No cancellations or refunds are permitted for
D23 Expo tickets. Tickets cannot be returned for any merchandise credit and have no cash value. The D23 Expo is not responsible for lost, stolen or forgotten tickets. For questions about the D23 Expo please contact customer service at
D23expo@experient-inc.com. Our guest service hours are Monday - Friday from 9 am - 5 pm EST. For questions about your D23 Membership or your membership number please email
guest.services@disneystore.com.