Hi Lorenzo,
If workflow creates new instance, you can not pass workflow container to new workflow instance.
If comments are stored in application table, you can retrieve it from application table. It is a job for workflow template side.
Your situation:
App comment -> Workfloe Container -> rejected and workflow instance is completed.
New event -> New workflow started -> New container does not have comments.
Solution:
App comment -> Workfloe Container -> workflow step saves comment in app table.
New event -> New workflow started ->workflow step reads data from app table -> pass to workflow container.
or
You can edit the workflow template for loop until approved. So new workflow instance won't be created and workflow container is available in the loop.
Regards,
Masa
SAP Customer Experience Group - CEG