So I do a header refresh, and half a dozen posts show up (everything else in the group is already marked old, and I have 'Hide Old' selected from the drop-down).
I right click a post, and select 'Mark All Old', and all the visible posts get marked old, but still display. I then right click and select 'Hide Old', and suddenly a few hundred posts get displayed, all already marked as old. I then right click and select 'Hide Old' again, and all the posts get hidden.
Surely that's not right?