Feeds disappear from the feed list (but not the feed view) when I read the last item; Ars was the latest victim. Fully-read feeds from before this began happening are not visible either. However, they are all still are listed on the OPML file.
Also, my Wolfram|Alpha feed seems to have a phantom unread item that has been there for days.
These problems are seen on two computers and three browsers.
My account is init2null. Thanks!
Go to Preferences (click the tiny gear icon in the lower left corner) and see the settings for Site sidebar. They are:
Show everything (what you seem to want)
Hide sites with no unread stories (what seems to be enabled right now)
Can’t believe I missed that when I was looking, but I’m sure I didn’t change that setting. Thanks!
You probably hit the “X Sites” button at the very top of your feed list. That’s the shortcut to switching between all/unread views.