If you're using an Automation rule or Incident rule it's really easy.
You should be able to add:
WORKITEM(workitem_comment) to the Workitem_comment section of whatever rules you're using to create the child sections.
The great part of it is you can add instructions as well. In our environment we're using it for a missing laptop scenario. We have an automation rule setup to generate 3 children tickets where we request various steps to be performed for each of the different teams involved.
Hope this helps.
edit: note this grabs the latest comment not necessarily the "First" comment