Noticed about a week ago that this seems to have stopped working.
It finally got fixed months ago after the forum upgrade so only topics with a mod time of greater than the last click of 'mark community as read' would show, but now again this click seems to be being ignored. I.e. all topics show when View New Content is clicked. After clicking “mark community as read”, there should be no new content unless there was a post after the “mark community as read” link was clicked.
It's working for me currently.
So if you click 'Mark community read" at he bottom of the page and then click View New Content at the top, you get no listings?
Yep works perfect for me from two different desktops and my mobile .
Why is it things always seem to work fine for you, but when I try them they don’t work? 
When I mark as read and then view new content it shows I have 26 pages of content to view.
That is odd did you try different desktop or browser for kicks?
Same behavior on my laptop and desktop (but same browser). How could it be browser related? It's a server function (data delivery).
I was just trying to suggest ways to test since its working for me .