We use the updated field as a way to tell if a ticket has been worked on but not all working requires a reply to the submitted. Comments should update the update field.
I think you're better off throwing support behind CHD-540 instead of your CHD-1245. The general request is more open-ended for a larger solution to tracking comment activity via ticket lists.
I considered it a bug report. To me it is a mistake that adding a comment doesn't update the updated field. If you called it last replied that would be diff. but you called it updated.
Bug
Closed
[Comment] Comment do not update the updated field.
