Len,
This is one area, I will admit, where the forum software in use there beats vBulletin *HANDS DOWN*. One of my only complaints about vBulletin (and many other packages out there) is how it handles the marking of threads read, and the displaying of new posts.
Unfortunately, without getting too technical, the best answer I can give you is "Not at this time". However I will add this to my "hack wishlist" and see if I can find a modification to implement something similar.
In the mean time, I will bring up another feature which you may also miss, being used to the Threaded view of the AOPA site. You can, at the top of any thread, change the
Display Mode to a threaded or hybrid mode. This will put the 'thread tree' for the post at the top of the screen and the bocy of the messages in the lower section. Its not quite like the other software, and in fact I think it's rather badly laid out and will work to improve that layout at a future date, but it is at least a way to easily tell what replies came from whom, and as long as you know when you were here last, you can see the list of replies and when they were posted and pick and choose.
Yeah, I know - not what you were hoping to hear...
CH