When you create a thread, it is supposed to show the actual text in the thread on the teaser when Teaser Post is set to "First"
It also does show the text in the teaser, but only when someone comments (It does not show the actual comment text)
There seems to be some kind of mismatch here. I'm watching two categories (General and Development); there's a "1 unread topic" bubble, but when I go to https://community.nodebb.org/unread, I get a "no unread topics" message.
Probably a very small error somewhere, but worthy of correcting.
It's gone away on its own after posting this thread -- but it shouldn't have been in that state to begin with, right?