I note a minor flaw in the posting tree display logic, as exemplified by this post. The poster left the title field blank, so the the display logic uses the post itself as its display token in the list. Since the post is quite a bit longer than what's typically available for a title, the tree display has an entry that extends far beyond the right border. That has the side effect of moving the vertical scrollbar off the screen and out of reach.
Hmm. That was weird. I edited that post (moved the first sentence into the title field).
Does that happen whenever you wipe out the default title and don't replace it with anything? I'm going to try it here.
Update: Yup, it does. Fixing now.