Now I kind of want to try my hand at implementing this. I imagine an implementation would add a buffer-local variable holding the position of the point as of the last non-scrolling operation. This would be updated in post-command-hook, but only if the last command was not a scrolling command (which would probably have to be defined as a list of "blacklisted" commands that shouldn't change the point). This hook would also hide the cursor if the desired position of the point is off-screen and show it otherwise. Finally, a pre-command-hook would set the real point to the saved position unless the command about to be executed is a scrolling command or a mouse interaction (which should move the point to somewhere on-screen).