Hi!

To navigate to the replies to a message, one has to scroll up and down to find the appropriate branch of the tree, which then moves the message just read out of sight.

I would like to mention an even more complex but in my opinion better solution for the threaded view.
Divide the viewport into two vertical arranged areas:

• Put the navigation at the top.
  
• Use a div at the bottom for the post content which will be loaded by AJAX calls according to navigation events.

This would result in a real usenet client experience. But I could imagine that this would be hard to implement.

Greetings,
Manuel