With PowerShell ISE:
If using a split view (showing both the console and script pane), re-focusing on the console from the script pane (or another console tab) will always scroll to the bottom.
To observe this effect, scroll up in the console so that the prompt at the bottom is hidden (obviously you'll need some output if you want to scroll up). At this point, you can click anywhere in the console to select and copy text. You can even leave focus from the ISE and click on your favorite web browser or text editor, and click back in the ISE console and the scroll doesn't change.
The problem is when you click in the script pane. The second you lose focus from the console within the ISE, you have sealed your fate. The instant you click black into the console, it will scroll to the very bottom! Clicking on another console tab will also scroll it to the bottom.
I made the graphic below just in case my description was confusing. The colored circles represent clicks. Green clicks do NOT cause the console to scroll. The orange click seals the fate for a red click, which will scroll the console.
This issue makes it impracticle to copy more than one item from the top of the console to the script pane, because you must scroll back up every time. You could copy everything into a separate text editor before pasting, but that is silly and almost equally impracticle.
I have tried using CTRL+I and CTRL+D to switch between the script pane and the console, but the same scrolling effect occurs.
I am using PowerShell 3 on Windows 7.