Currently, thread list is sorted by mod_date of internal thread object. mod_date is updated on some administrative actions, like thread moderation, so thread order may change unexpectedly to users. This was discussed on the mailing list and it was decided that it's worth to add "last post date" field to a thread object and sort based on that.
On rc/1565
To QA: create a thread. Create a second thread. Label the first thread. Verify that the second thread is still the most recent under "Recent Topics" in the sidebar.
Diff:
Related
Tickets:
#1560Trying to assign to kadams didn't work, now trying kadams54
Looks good.