If I'm not mistaken, this kind of crap is why some people are PO at the thread-sorting option for date-of-post rather than date-of-reply being removed, basically "just because" (Jason didn't think enough people used it). :roll:
Anyway, there's no way to tell date of post (unless it's in the title, or subtitle now) unless you open the thread, which I could see as being frustrating to a dialupper (being one myself).
Sorry Quackagator, but I don't think there's a simple solution to your problem. 🙁