I'd report this as a bug, but I'm sure the current design is intentional, I just want to discuss it and see what others think.
When you go into your personal conversations page either through clicking the 'read' button in the new message notification at the top of the page, or by clicking the link in your member dropdown, the focus is automatically set to the posting textarea. I can see why this is done, so that you can just start writing, but a side effect of this is that the navigation keys on your keyboard (Home, End, Page Up, Page Down) no longer will scroll the page; you have to click outside of the textarea to be able to use those again. I've been caught by this more than once, and it's a little annoying.
Is it just something we'll have to get used to?