I'm not so sure about that Ian,
Because, I do have the habit of clicking on that button ..''unread posts since my last visit''
But when it shows blank, I think its time for me to retire for the evening...HOWEVER....last night, it was blank .....but there was quite a few postings listed at the bottom of the home page which I had never seen, including replies to MY postings.
I shall keep an eye on this, and report back accordingly.
If I am wrong, I shall let you know, if only for the sake of courtesy.