Comment 24 for bug 115153

> Has anyone come up with a reason why people might ever want to sort by the
> date/time a file has arrived in a folder?

I'm speculating that this happened primarily because the developers of the Netscape era were dogfooding with IMAP, where (if I understand this correctly) "order received" *is* "date received" even for messages moved to folders.

Similarly, Order Received is the tiebreaker for all other sort criteria -- subject, sender, whatever (xref bug 363991). Arguably, that should be "by date" as well.

Also: it used to be that threads sorted by date used the date of the topmost item in the thread, so sorting by date didn't necessarily gain you anything in terms of visibility of recent messages -- in which case, sorting by Order Received isn't much worse. That behavior was changed (around the time of Mozilla 1.5, I think) to use the most-recent item in the thread. (Bug 254159 seeks the same technique for using Order Received sorting.)

Even sorting by date is contentious -- see bug 166254. A lot of people want sort by "Received Date" because Date headers are often broken; others want the Date header to always be used.

Anyway, Gerv: the patch at bug contains the line that sets the sort criterion for sort-by-thread with unthreads=False:
  sortType = nsMsgViewSortType.byId;
If you want to submit a patch and drive it past the gauntlet, more power to you.