Yes and that is what I did. But it is not easy, and 99% of users just used sent mail. And even when done it does not group related messages. So no, not close to the GMail threading.
I actually do not think that there was a single widely used EMail system that supported threading in the way No News did.
What is sad is that labels and threading are the type of features added by smart engineers in small teams, which is what GMail would have been long ago. But it is not the sort of thing that the MBAs that run large teams would do. They do cost benefit analysis, end user surveys, study the in flight magazines and thereby attempt to create a faster horse. Hence all the changes to GMail in the last 10 years are cosmetic rubbish following fashions, often making the actual email harder to read (e.g. picking apart long threads). Products generally have a short initial innovative phase, and then if they are successful they are squashed by management.
I think that whatever Inbox turns out to be it will be the end of GMail for me.