Unless I am missing something, I'm not sure how this isn't a top rated ticket. But resolved cases need to be editable via API and workflows. Every other Entity allows you to edit deactivated Leads, or Opportunities or Custom Entities. For some reason they treated cases differently.
Category: Case Management
Ideas Administrator

Thanks for your feedback. Updates to resolved and canceled cases are allowed using API and workflow.
Please refer to the following link for more information - https://learn.microsoft.com/en-us/dynamics365/customer-service/update-resolved-canceled-cases