None of the personal settings available to us at present can be used to permanently sort our Thread views on "Thread Start Time".
I'm not sure whether or not that ability could be added for us during a future upgrade. My guess is that it isn't something the software could provide. Still, I will try to remember to ask the tech team. It's a very constructive suggestion, so thanks for asking.
Since upgrades are labor-intensive and take us offline for a few hours each time they are incorporated, they won't happen very often. So, if they can make a personal setting like that available to us, it will be a while from now before we see it.