In 1.5? I highly doubt it.
I use osTicket for a year and a half, and not the 1.5 version. ;-)
The version I'm using is the v1.6 ST.
As for my need I wish that when the user clicks on "Reply" to send a reply, the ticket takes, automatically high priority.
There is a change ready to do this?
I unfortunately do not know programming in PHP.
Circumstances, it may be helpful to understand which file to edit to try by yourself.