So the sequence for any one thread is:
a) new thread created.
b) thread appears in Feedreader.
c) I link through and read the thread as it stands at that instant.
The thread will never appear again in Feedreader. If I manually read the thread I may find new posts (that I have never seen before) and if I go back to Feedreader there is nothing despite the last update being after the date posted of new posts.