I see that, too. If I refresh the page the threads are all marked read.
There is now a dialog box that comes up telling you that you just marked all threads read. DUH! as the young people used to say. That's a pointless step, an insecurely nagging need to be clicked.
Further (and this has been true from the beginning of Huddler), "marking forums read" presents "This forum or all forums?". Since we're reading "this forum" that is the one to clear. Just do it silently, no confirmation needed.