Huge arrow and black spot? Are you certain that is not a setting in your mouse (if you're using a mouse)? I don't see this.

Yes I'm certain.
Checking "for mouse wheel clicks" and immediately a rather big arrow appears after a mid-click pointing to the direction of the mouse movement. Increasing the movement (= increasing speed) additionally a black spot appears in a distance to the arrow proportional to the speed.

Here's a screenshot but the black spot (about the same diameter as the arrow) seems not to be "screenshotable"