The default field order does not always make sense.

I think we should first have Category and Status, then Severity and Priority, then whatever, and finally, just before the summary Privacy and Discussion Lock.

I dont know exactly where Assigned To and Open/Closed should be. Maybe just after Severity and Priority, or even just before (well, just after would make sense as only trackers managers can alter these fields, and are so as secondary by comparison to Severity and Priority).