There might be a way to fulfill your requirement.
1.Create a custom record with a text area field, List/record type field for employee (commenter) , date and a custom list field to show escalation stage and a list/record field to reference the related case.
2.Use a workflow for approval for the case record. When case need to be escalated it should enter one of the escalation states (no of states depended on your requirements) - use a go to record action to open the custom record form in edit mode and sourced field values from the case record via workflow. Let the user enter the escalation message and save the record - at that point case record would be escalated by the workflow. Repeat the same process for the escalation stages.
3. Create a saved search for the custom record, with filter for related case: Internal ID and save it as available for sublist. Create a sublist for case record and show this search - it will show the commenter's name along with messages as sublist in the case record. You can also use this search to source the messages to a custom field in case record too.
There are 100 ways to skin a cat, just play with it, it should work.