Probably should be something i address to Site Moderator's as at least in the prior version of the software new comments made, irrespective if you were replying specifically to a comment in a thread or just a general comment (at least anectodally) i found always updated the overal Topic thread chronologically.
I can see that in at least this one example from this morning that did not occur, as the new comment is visible when i go back to the original thread but didn't make it to the most recent Topic page in the Deli section.