What does this enhancement do?
Currently, for the ticket view, the display simply maintains the ticket itself, and then a listing of the comments from most recent to least recent.
It would be a great addition to add a installation-wide option in the AdminCP to choose whether comments are displayed newest to oldest or oldest to newest.
Most bug tracker software which I have had experience using with the exception of Traq tends towards the chronological posting, allowing for a sequential reading flow as opposed to the jumping around which occurs when the comments are placed out of sequence when displayed in reverse order.
Beyond the enhancement, I would further submit the recommendation to have the chronological display of comments become the default ordering.