The feed is not currently configurable/able to be defaulted to enabled when printing a ticket. I would imagine it is disabled by default in the use case that the full feed contents might not always be wanted to be printed, so rather than always include it, we exclude it and make sure the users really want it to be printed by manually checking to add it.
This might be a great feature to request though. You could request this feature via our Client Portal Home page by clicking on the "Request a feature" button. If the same request does exist already from another requestor, we will group your enhancement with the existing one so we can keep an eye on the number of requests the feature has.
Please let me know if you have any additional questions.