As of this afternoon a load of old threads have appeared in the thread list. They are all full read and are appearing under the "Unread Discussions" option.
There are two in technical, four in general, one in coding and one in beehive development.
They all have a time next to them of 14:24. Going to the last post of the thread doesn't render them read. Well, actually, it seem Beehive knows they are read because the icon next to them is the small dot instead of the bee.