Are you sure? I would think you can set conditions in the first part of the SLA to target only tickets with a certain form or field (IE one that indicates it is an internal ticket based on your usecase/workflow).

I don't know off the top of my head if you can filter by internal comments, but if so that would probably help you even more.

If you're still stuck send a ticket to [[email protected]](mailto:[email protected]) after you've done some research and have an idea of if the above is true/will accomplish your workflow or not. They are super helpful, especially if you have a well organized question and have done some research on it.