Having looked a bit more at the Feed page I find myself wondering if there is an inherent limitation as it currently stands; I have started a new topic rather than bolt this on to a thread that is already enormously long.
Each of an Account Holder's groups shows "Active Topics", and it looks as though "Active" is defined as those 5 topics to which posts have been sent most recently. An effect of this is to push a perhaps busy topic down the list to the point where it falls off the bottom purely on the basis that there have been posts to 5 other topics since the "busy" one received a post.
Any Subscriber working solely from the Feed might easily miss what is still an active topic because it has been pushed off the bottom of the list; OK it might pop up again sometime later, but again it may not. In the meantime unless our specimen subscriber goes to Topics view the posts to the "busy" topic risk not being seen.
I know that there has to be a cut - off for inclusion in the Active Topics list, but I wonder if 5 is the correct number. My own preferred starting point is the My Groups list, and a quick glance at the times visible on that page, along with the times for the most recent posting on any topic on any given group tells me where to look for anything new. As currently formatted the Feed page may mislead subscribers into believing that the lists presented there are all they need to catch up since they last visited, and that may very well not be true.
In case anyone is wondering I must stress that I am not arguing against the existence of the Feed page, merely querying if the limit of 5 Active Topics is necessarily appropriate or if it is potentially misleading.