Crudely observed, in threads where posts are out of sequence, the "first post" usually seems to appear at about the 6th to 8th position or so. This may be helpful when you need to sort things out, although I haven't run any statistics on it to determine whether it's always that way.

If you really need to figure out a long thread, you can copy the list at the top, paste into Word as "unformatted" (Edit | Paste Special | unformatted text), and sort the list on the date/time columns; but that gets tedious unless it really matters. You have to do a bit of "dressing up" of the pasted text to separate the columns for sorting.

In longer threads, there appear to be some places where "out of order" posts sort of "cluster," but I haven't tried to see if there's a general rule for where it happens.

John