Eclipse Mars introduce a terribly annoying feature that you can’t even turn off, sigh. If you now scroll up in the console Eclipse automatically activates scroll-lock. Hence, if you just browse the console output scroll-lock will be ON when you’re down browsing and leave the console. How awful is that?
The implementation was triggered by bug 149393 from 2006(!).
If you’re adventurous here’s the commit you’d have to revert or otherwise modify to get the old behavior back: http://git.eclipse.org/c/platform/eclipse.platform.debug.git/commit/?id=a11ed20c73670c89c15179e9f790f53ac7e31c33